UNIVERSITY OF CALIFORNIA COLLEGE OF AGRICULTURE AGRICULTURAL EXPERIMENT STATION BERKELEY, CALIFORNIA CIRCULAR 334 June, 1934 SOILS AND CROPS OF THE IMPERIAL VALLEY STANLEY W. COSBY 1 and L. GORDON GOAR 2 Imperial Valley is supplied with gravity-flow water from the Colorado River. This is one of the main irrigation canals. INTRODUCTION The "Imperial Valley" — a depression below sea level in the great Colo- rado Desert — has become a nationally famous agricultural district within the short span of three decades. Thirty years ago it was uninhab- ited. Today it is occupied by sixty thousand settlers who cultivate more than four hundred thousand acres and annually produce twenty-five million dollars worth of farm products, the greater portion of which is marketed in the large population centers of the central and eastern states. Figure 1 shows the railroad facilities of the Valley. 1 Assistant Soil Technologist in the Experiment Station. 2 Associate in the Experiment Station. 2 University of California — Experiment Station The rapid transformation was made possible by the diversion of water from the Colorado River to this arid basin, in which there had pre- viously been no adequate supply even for domestic use. The availability RAILROADS. N/LAND \ r . • • ;| ? §- ) Esfe//e \ ^S. \^CALIPATRtA \ ^ '*•»... Qr~ondo-, > ) Bern ice 72/^v \ — V Casa6-ci ' . L WESTMORELAND 1 H<0od( » > Munyon\ I i O Moss v L, j Obrawley l „ ya \ , • / A Curlew • \ 1 r ' t y # .S J //MPERIAL Q \ L 6 Sand/a j * $ \ f 1 A tin i i *» « a \ "; <$ \ A < V \ \ V '.. ] 1 J \ £AL £"A7<70 : r • 1 _ — — — ■* — Fig. 1. — Railroad facilities in the Imperial Valley. Cities and towns are indicated by capital letters and rural shipping points by smaller type. of water, the smoothly sloping land surface, the almost complete absence of crop-damaging rains, and the relatively high temperatures during the cooler seasons of the year, were advantages which quickly attracted many settlers. These came from nearly every state in the Union and Cm. 334] Soils and Crops of Imperial Valley 3 from numerous foreign countries. Many kinds of crops were introduced with varying degrees of success, new farming practices were developed to meet the distinctive conditions of an unfamiliar environment, and every effort was made to utilize fully the climatic advantages of the district. However, as occurs in most pioneer communities of similarly dynamic character, the suitability of the soils for the crops which were planted received little or no consideration. Until recently, the farmers of the Valley appear to have planted the crops of their choice with little or no regard for the types of soil involved. The difficulties of crop production in this transformed desert devel- oped the need for new methods and practices, and resulted in an early demand that an experiment station be established for the purpose of scientific investigation of the culture of various economic crops for this and adjacent areas. Consequently, in 1908, the State Legislature passed a bill providing for the establishment of a branch agricultural experi- ment station for the Valley. Through the cooperation of the Imperial County Board of Supervisors and of interested private citizens, the Imperial Valley Experiment Station was established at Meloland in 1912. This farm now contains 40 acres, and was secured in 10-acre blocks at various times between 1910 and 1914. It was deeded to the Regents of the University of California, and since 1913 has been under the admin- istration of the Agronomy Division of the College of Agriculture. The results of some of the investigations have been published from time to time as circulars and as special articles in scientific or popular periodi- cals, but no recent comprehensive report on the Imperial Valley has been prepared. At present, with the pioneer period of rapid development drawing to a close and agriculture in the Valley beginning an era of more intensive and better-planned operations, there is obvious need for a single, com- prehensive publication covering the more significant information so far secured regarding the soils, crops, and cultural methods in this unique agricultural community. It is the purpose of this circular to meet that need, and to give, in addition to an exposition of the natural conditions, the results of a study of the extent and character of the use of the lands of the region and a discussion of the crops that are or may be of economic importance. 3 3 A discussion of plant diseases and pest control will not be included in this cir- cular, as much information on these subjects is available in various bulletins and circulars that can be had by applying to the College of Agriculture, University of California, Berkeley, or to the County Farm Advisor. University of California — Experiment Station CLIMATE The climate of the Imperial Valley is that of a low-latitude desert. It is characterized by relatively high temperatures throughout the year, with long and exceptionally hot summers, low humidity and high rate of evaporation, a large number of days of intense sunshine, and an almost negligible precipitation. Although within 100 miles of San Diego with its equable coastal climate, the intervening barrier of the Peninsula range shuts off the moderating influence of the ocean, while to the east of the Valley lie desert slopes broken by barren rocky mountain blocks. Temperatures of 100° P or more are recorded for the months of March to October inclu- sive, and in each of the winter months temperatures have risen to 85°. A maximum temperature of 118° has been recorded for both May and June, and 115° for July and August; while the absolute minimums for these months are 41°, 51°, 57°, and 60°, respectively. The winters are short and mild with a large percentage of sunshiny days. Killing frosts seldom occur before the middle of November or after the middle of March; usually the period during which they may occur is from December 1 to February 15, and a frost-free growing season of about 300 days is normally expected. The lowest recorded tem- peratures are 21° F at Calexico and 20° at Brawley. The relative atmospheric humidity is low during the greater part of the year, a circumstance that explains why the summer temperatures, although reaching unusual heights, are not unbearable. In a recorded three-year period, 1904-1906, the evaporation from a free water sur- face at Calexico averaged nearly 7 feet per year. This high rate has been lowered somewhat, because of a greatly increased acreage of irrigated crops, and is now about 5 feet per annum. 4 The atmospheric humidity is higher during the winter and spring months than during the remainder of the year, although an exception to this general trend is supplied by the short periods of relatively high humidity which are associated with the erratic rains of late summer and autumn. Because of their very irregular occurrence and the small amounts of water which fall, rains in the Imperial Valley are seldom beneficial and occasionally they are detrimental to crops. The annual rainfall is de- cidedly low, the average at Calexico being only 3.10 inches and that at Brawley only 2.44 inches. In 1905, an unprecedentedly wet year, a precipitation of 9.33 inches was recorded at Calexico, while only 0.64 inch fell during the dry year of 1910. Although some of the summer 4 Calculated on the basis of the relatively stationary area of the Salton Sea and the amount of inflow of all waters. Cm. 334] Soils and Crops of Imperial Valley rainstorms arise in the Gulf of California to the southward, most of the rain-bearing winds come from the Pacific Ocean at the west. In crossing over the Peninsula range, however, these winds are cooled to such an extent that they precipitate much of their moisture on the high west- ward-facing slopes. Subsequently, descending the eastern side they are warmed and their capacity for holding moisture is greatly increased. They usually pass over the desert basin as hot arid winds, absorbing moisture rather than precipitating it. TABLE 1 Mean Monthly and Annual Temperatures and Precipitation for Brawley* and Imperial! (From records of U. S. Weather Bureau Stations at Imperial and Brawley) Brawley (119 feet below sea level) Temperature Precipitation Imperial (65 feet below sea level) Temperature Precipitation January February March April May June July August September October November. December. degrees Fahr 52.8 55.8 62.2 69.1 73 4 84.2 89.6 89.2 83 71.2 60 8 50.2 inches 0.41 29 24 0.14 0.07 0.01 0.07 0.16 0.11 0.17 14 63 Fahr. 53.0 58.9 65.0 inches 0.29 0.88 0.20 15 0.05 0.00 10 0.29 26 0.16 0.18 1.09 Annual. 70.3 2 44 71.9 3.65 * Length of record for Brawley, 24 years. t Length of record for Imperial, 12 years. The least pleasant weather of the year usually occurs during July and August, when brief periods of high humidity (due to overcast skies or the proximity of thunderstorms) are combined with the high tempera- tures of that season. Changes in humidity and in wind velocity occur suddenly, while rapid changes in temperature may be of frequent oc- currence. Winds of high velocity also may occur frequently during March and April. These are prevailingly from the west, and are not uncommon in the autumn as well, although strong winds may be ex- pected at any season of the year. Except for these occasional windstorms, there is nothing to mar a delightful and invigorating winter climate. Everything considered, the climatic conditions in the Valley are almost ideal for crop production; the exceptionally long growing season is of distinct advantage and constitutes one of the outstanding assets of the region. See table 1. University of California — Experiment Station THE SOIL MATERIAL Owing to the relatively recent origin of the deposits from which the soils of the Valley have been formed, together with the relationship existing between the soils and the land forms, it is deemed desirable to precede the detailed discussion of soil types with a brief consideration of the probable geologic history of the basin. As shown in figure 2, the land- ward portion of the great structural trough occupied in part by the Gulf of California extends northwestward about 200 miles across the desert of southeastern California. This terrestrial portion of the trough is divisible into (1) the Mexican section of the Colorado River delta fan; (2) the United States section of the fan, or the "Imperial Valley"; (3) a saline lake, "Salton Sea"; and (4) the Coachella Valley. The trough terminates at the northwest in San Gorgonio Pass, which leads toward the coastal section of southern California. The crest of the river- built barrier across the trough, slopes from an elevation of more than 100 feet in the vicinity of Yuma, Arizona, to about 30 feet at the base of Cerro Prieto, an outlier of the Cocopah Mountains. The enclosed basin to the north of this barrier drops to a depth of more than 250 feet below sea level. It is flanked on the west by mountains which reach to heights of 10,000 feet, while on the northeast it is bordered by a series of low mountains and hills which extend southeasterly in a slightly inter- rupted band to the neighborhood of the Colorado River. To the east and to the west of Imperial Valley, between the higher elevations and the basin proper, are two desert plains locally known as the East Side Mesa and the West Side Mesa. Roughly marking the inner limit of the mesa land, an old beach line nearly encircles the basin at about the 30-foot contour and delineates a prehistoric lake of considerable size. Geologic History of the Basin. — Since the middle of the last cen- tury, when the first geological information regarding this region was obtained, 5 the generally offered explanation for the formation of the basin has been that the portion of the basin which lies below sea level was occupied formerly by the Gulf of California, and that the Colorado River deposited enormous amounts of sediment in the gulf and built a barrier across it, isolating a great body of sea water as a lake. During periods in which the river flowed down the southward slope of the delta barrier, the lake to the north gradually evaporated to leave a dry, below-sea-level basin. In intervening periods the river flowed north- ward into the basin, filling it with sediment-laden waters before again s Blake, W. P. Eeport of geological reconnaissance in California. H. Bailliere, New York and London. 1858. Cm. 334] Soils and Crops of Imperial Valley turning southward. Such processes were presumed to have been re- peated many times. Recent investigations by Buwalda and Stanton 6 suggest an important Fig. 2. — Delta of the Colorado Eiver (stippled area) and its relation to the ad- jacent topographic features. The Imperial Valley occupies the delta area between the International Boundary and the Salton Sea. modification of one feature in the foregoing explanation. Their study of the Indio Hills leads them to conclude that "it is much more probable that the depression of the present Salton Basin below sea level has occurred during or since the building of the delta or cone, not before, 6 Buwalda, John P., and W. Layton Stanton. Geological events in the history of the Indio Hills and the Salton Basin, southern California. Science 71:104-106. 1930. 8 University of California — Experiment Station and long after the invasion by the sea," and that the basin was not occu- pied by the salt waters of the gulf. This conclusion is further supported by several considerations. The delta deposit is extremely young, un- doubtedly Quaternary in age. As the lowest point at which the sea could enter the basin (i.e., the western part of the delta crest) is only 30 feet above sea level, it is extremely probable that the basin would remain coupled with the gulf until the last 30 feet of material began to be added. Thus, the latest presence of sea water in the basin would be an event of very recent geological time. It is significant from this stand- point that, although there are excellent exposures of recent fresh-water deposits, there are no reported marine beds within the basin which are youthful or which bear expectable relations to the sea-level contour. Moreover, the old beach line of the fresh-water lake is a conspicuous feature, but no marine terraces or strands have been noted. The occur- rences of marine strata of the Carrizo formation at elevations of hun- dreds of feet above sea level, together with their strongly folded and beveled character, indicate that they were not deposited during a possi- ble occupancy of the present basin by the sea, but in an earlier depres- sion of considerably different form which existed long before the present basin came into existence. And finally, Ross 7 has shown that the accumulations of salt in the basin were derived in all probability through the evaporation of water from the Colorado River, and not from a cut-off arm of the ocean. The presence of an almost continuous, fresh-water beach encircling the basin at approximately the same elevation as the low point of the delta barrier is provocative of further consideration. The essential con- tinuity of this easily destroyed feature is evidence of its relatively recent origin. Its degree of development and the absence of other paralleling beach lines suggest that the lake remained at a more or less constant level for a considerable period of time. This constancy of surface level could have been achieved in two ways : the inflow from the Colorado River may have been equalized by evaporation from the extensive water surface, or an equilibrium may have been maintained in part through the medium of an outlet which carried the excess water to the sea. Of these possibilities, the second appears more probable. The recent origin of the beach suggests a possible conformity with some other surface feature not yet obliterated, while its elevation directs attention to the low point of the delta divide. At that point originate the New and Hardy rivers, the first flowing northward into the basin and " Ross, W. H. Chemical composition of the water of the Salton Sea and its annual variation in concentration 1906-1911. In: Carnegie Institution of Washington Pub- lication 193:35-46. 1914. Cm. 334] Soils and Crops of Imperial Valley 9 the second southward into the gulf. The headwaters of both streams are poorly defined and to some degree connected. If the southward flowing Hardy River represents such an outlet for the excess water of the lake as postulated and if the inflow channel from the Colorado River was situ- ated approximately along the present course of the Alamo River, it would have been possible for a lake to be maintained in the basin for a brief but sufficient length of time to have produced a beach line at ap- proximately the elevation in question. Owing to the soft character of the material, headward erosion prob- ably would have been rapid along the outlet channel and this may have led to a relatively sudden lowering of the lake level. Such a process would afford a partial explanation for the absence of other conspicuous beach lines within the basin. Origin of the Soil Material. — There is little doubt that a large part of the material on the northern slope of the delta fan was deposited under lacustrine, or semi-lacustrine circumstances. The relatively uni- form fineness of the material, the almost complete absence of gravel or other coarse particles, and the occurrence of this homogeneous material in strata which are parted by almost indistinguishable laminae of aeolian sand, tend to support such a conclusion. A close inspection of these de- posits, as exposed in the deep cuts along the New and Alamo rivers from the International Boundary northward to the vicinity of Salton Sea, reveals an increasing proportion of colloidal material and a thickening of the strata as the Salton Sea is approached. These conditions suggest the possibility of the lower-lying material (i.e., that nearest to Salton Sea) having been deposited under more truly lacustrine conditions than those which obtained higher up on the delta slope. Since the dissipation of the lake that formed the beach line about the basin, the Colorado River has flowed from time to time down the northern slope. Such inflows are reported to have occurred in 1840, 1849, 1852, 1859, 1862, and 1867, 8 not to mention the devastating and pro- longed incursion of the river in 1905-07. Although none of these later inflows appear to have had the magnitude or the persistence of that which resulted in the ancient lake, some of them undoubtedly produced bodies of water in the lower part of the basin which were somewhat comparable to the present Salton Sea. With the river diverted again to the gulf, these bodies of water dried up and the last of the suspended matter was deposited. In contrast to these lacustrine deposits in the lower part of the basin, those occupying the aerial, or upper, portion of the delta slope are, to a considerable degree, made up of river-deposited s Cory, H. T. Irrigation and river control in the Colorado River delta. Paper 1270. Transactions of the American Society of Civil Engineers 76:1204-1453. 1913. 10 University of California — Experiment Station sediments and probably were more subject to aeolian influence. Aeolian or windblown sands that might have drifted into the basin during a period of dessication would be washed about and redeposited by river flow and wave action. The sandy deposits south of Holtville show strik- ingly this condition of deposition. River and windborne materials make up most of the sandy soils of the basin. More than two-thirds of the present surface of the basin is made up of heavy-textured sediments, mainly of lacustrine deposition. SOILS OF THE IMPERIAL VALLEY Four soil surveys have been made in the Imperial Valley, and reports covering them have been published by the U. S. Bureau of Soils. The first 9 was made in the latter part of 1901, at the beginning of settlement in the area, and the second 10 during the winter of 1903. These two early surveys embrace a total area of 1,084 square miles in a single tract, extending from the International Boundary northward to the site of the present Salton Sea and reaching across the valley trough from the eastern to the western beach line. In this relatively large area only seven types of soil were differentiated and five of these were considered to be textural variants of a single series. This simple classification suggests the marked similarity in general characteristics which exists between these soils. A third survey 11 was made in the winter of 1918, while the fourth and latest 12 followed in the winters of 1919 and 1920. The third survey cov- ered the southern portion of the Valley, while the fourth embraced all of the remaining land in the Valley that was considered irrigable from the canal systems. Each included portions of the contiguous mesa lands. These two surveys, comprising an aggregate area of 1,151 square miles, were made under the cooperative agreement entered into about 1913 between the U. S. Bureau of Soils and the College of Agriculture, Uni- versity of California. At the time these surveys were undertaken, many basic principles of soil morphology and taxonomy were more clearly understood than in earlier years, and the soils were studied more criti- cally and mapped in greater detail. For these reasons, and also because portions of the bordering mesa land were included, the number of soil 9 Means, T. H., and J. Garnett Holmes. Soil survey around Imperial, California. Field Operations of the Bureau of Soils. U. S. Dept. Agr., 1901. p. 587-606. !o Holmes, J. Garnett, et al. Soil Survey of the Imperial area, California. Field Operations of the Bureau of Soils. U. S. Dept. Agr., 1903. p. 1219-1248. 11 Strahorn, A. T., et al. Soil survey of the El Centro area, California. Field Op- erations of the Bureau of Soils. U. S. Dept. Agr. 1918. p. 1633-1687. 12 Kocher, A. E., et al. Soil survey of the Brawley area, California. Field Opera- tions of the Bureau of Soils. U. S. Dept. Agr. 1920. p. 641-716. Cir. 334] Soils and Crops of Imperial Valley 11 TABLE 2 Extent of Soil Types Mapped in El Centro and Brawley Areas Soil Valley or basin soils: Imperial very fine sandy loam Imperial loam Imperial clay loam Imperial silty clay loam Imperial silty clay Imperial clay Meloland gravelly sand Meloland fine sand Meloland fine sandy loam Holtville very fine sandy loam Holtville loam Holtville silty clay loam Holtville silty clay Holtville clay Rositas gravelly fine sand Rositas sand Rositas fine sand Rositas very fine sand Rositas very fine sandy loam Woodrow fine sandy loam Woodrow clay Dunesand Total, valley or basin area Mesa or valley-margin soils: Niland gravelly sand Niland gravelly fine sand Niland gravelly clay loam Superstition gravelly coarse sand Superstition gravelly sand Superstition coarse sand Superstition sand Superstition fine sand Tijeras gravelly sandy loam Tijeras gravelly fine sandy loam Tijeras gravelly clay Carrizo sand Total, mesa or valley-margin area Miscellaneous waste land : Rough stony land Rough broken land Riverwash Total, miscellaneous waste land.... Grand total, area Acres 2,176 4,544 9,536 19,776 107,008 103,616 4,096 20,736 54,464 9,600 5,248 41,536 81,984 46,144 1,472 4,544 24,832 17,024 9,792 1,984 1,152 17,024 588,288 ,520 ,592 ,656 ,104 ,648 ,304 ,264 960 ,392 ,344 ,912 ,504 3,328 12,416 8,064 23,808 713,600 100.0 Per cent Per cent of total of regional area area 0.3 0.4 06 0.8 1.3 1.6 2.9 3.3 15.0 18.2 14.5 17.6 0.6 0.7 2.9 3.5 7.6 9.3 1.4 1.6 0.6 0.9 5.8 7.1 11.5 13.9 6.5 7.8 0.2 0.3 0.6 8 3.5 4.2 2.4 2.9 1.4 1.7 0.3 3 0.2 0.2 2.4 2 9 82.5 100.0 3 3 23.4 1.6 11.4 09 6.5 0.9 6.6 3.2 22.8 0.5 3.6 0.3 2 2 1.6 11.1 0.1 0.9 0.5 3 3 0.2 1.3 1.0 6.8 14.1 100.0 0.5 14 1.8 52.1 1.1 33.9 3.4 100.0 ■ types increased to thirty-seven. Twelve of these are members of the Superstition, Niland, Tijeras, and Carrizo series, which occur almost exclusively on the mesas, while three others — rough stony land, rough broken land, and riverwash — comprise miscellaneous materials of 12 University of California — Experiment Station little or no pedologic or agronomic importance. Twenty-one of the re- maining twenty-two types are members of the Imperial, Meloland, Holt- ville, Rositas, and Woodrow series, while the twenty-second is dunesand (a classification which is normally considered as a miscellaneous non- agricultural type, but which in this locality is subject to leveling and use for crops). The total and proportional areas of these several types of soil are shown in table 2. The Imperial, Meloland, Holtville, and Rositas series are the four more extensive series mapped in the two later surveys. They almost completely dominate the central and more readily irrigated portion of the Valley and include all of the soil types which are now being used to any important extent for agricultural purposes. All four have their origin in the deltaic sediments of the Colorado River and furthermore, with the exception of the inextensive Woodrow series, they constitute the only soils in the two surveys which have so originated. These four series of soils have the following profile characteristics. The Imperial Series. — The Imperial series consists of a light brown- ish gray to light chocolate brown, fine-textured surface soil that grades imperceptibly into a compact, relatively impervious, fine-textured sub- soil of similar character. Both surface and subsoil are calcareous and have a very low content of organic matter. When thoroughly dry the surface soil has a definitely grayish cast, but when wet it is a light chocolate brown with a purplish or reddish cast. 13 The subsoil is of the same or slightly lighter color, and in places it is faintly mottled with grayish or reddish stains. Except where concentrations of alkali have resulted in a characteristic "crust and mulch" structure, the surface soils are typically single grained. In most cases the coarser textures are more or less friable, whereas the finer ones are compact and somewhat puddled. The subsoil is characterized by a massive, jointed, or somewhat shale-like structure, the latter generally occurring where the subsoil consists of numerous thin strata and laminae. Six types of the series were mapped in the surveys of 1918-1920. Three of them are not extensive and to some degree represent modifica- tions of other types. The very fine sandy loam occurs in a limited number is Colorimetric determinations were made recently by C. F. Shaw of surface sam- ples of six types of soil from the Imperial Valley. These six types and the percentages of white, black, yellow, and red (in that order) were as follows: Holtville silt loam, 22-41-17-20; Holtville silty clay loam, 20-41-19-20; Holtville clay, 23-37-21-19; Imperial silt loam, 22-41-17-20; Imperial silty clay loam, 23-41-17-19; and Im- perial clay, 20-41-18-21. On the basis of recommended color designations in the 1927 report of the Color Standards Committee of the American Soil Survey Association (Bulletin IX, March, 1928) Shaw suggests that the color of these soils be desig- nated as a "light purplish gray." Cm. 334] Soils and Crops of Imperial Valley 13 of small strips just south of Brawley and along the Alamo River near Salton Sea, where it represents an extremely recent surface deposit of alluvium. The loam, likewise of small extent, is rarely encountered in virgin localities and commonly represents a surface addition of fine sediment brought in by the irrigation water. The clay loam also is local- ized, and, like the loam, is largely a product of irrigation with sediment- laden water. The three remaining types — silty clay loam, silty clay, and clay — constitute nearly 33 per cent of the total area surveyed. Each of the three occurs in numerous bodies distributed over the floor of the Val- ley and represents alluvial or lacustrine deposits of notably fine texture. All three are typically compact and more or less impervious throughout. As mapped in these surveys, however, the silty clay and clay types in- clude areas which have strata of fine sand and fine sandy loam within the subsoil, these pervious strata being distinctly and sharply defined from the layers of clay. Such nontypical areas represent a soil inter- mediate in character between the soils of the Imperial and Holtville series. The Meloland Series. — The Meloland series consists of a light brownish gray to light grayish brown, pervious, coarse-textured surface layer overlying a compact and relatively impervious, fine-textured sub- soil having a slightly browner color. Both surface soil and subsoil are calcareous and very low in organic matter. The subsoils are essentially identical with those of the Imperial series. The surface soils are dis- tinctly different, however, and this difference constitutes a basis of separation. Typically, the Meloland surface soils consist of medium to fine sands with a very small admixture of silt and clay. This material is particularly loose and friable, and under virgin conditions the surface configuration of the Meloland soils affords definite evidence of aeolian influence. Three types of the Meloland series were mapped — gravelly sand, fine sand, and fine sandy loam. The gravelly sand not only is of small extent, but also is to a degree nontypical of the series. It occurs exclusively to the south of Superstition Mountain near the ancient beach line, and in certain characteristics the type approaches the soils of the Superstition series with which it is associated. The fine sand is of somewhat wider occurrence and, although it shows the influence of associated bodies of dunesand, this type is more nearly representative of the Meloland series. The fine sandy loam, which is typical of the series, is widely distributed throughout the southern, western, and central portions of the Valley; it occupies nearly 8 per cent of the area surveyed. This type includes some bodies having pervious strata of fine sand and fine sandy loam within the normally compact clay subsoil. These represent a condition inter- 14 University of California — Experiment Station mediate between the typical soils of the Meloland series and those of the Rositas series. The Holtville Series. — The soils of the Holtville series consist of a light brownish gray to light chocolate brown fine-textured surface layer overlying loose and relatively pervious, coarse-textured subsoil of simi- lar or slightly lighter color. Both surface soil and subsoil are calcareous and contain little organic matter. Type for type, the surface soils of the Holtville series are identical with those of the Imperial. The subsoils are notably different, however, the difference constituting the major basis for separating the two series. The Holtville subsoils consist of loose and, in places, stratified deposits of fine sand and fine sandy loam together with incidental thin layers or lenses of still finer material. Five types of the Holtville series were mapped in the Imperial Valley. Two of these, like three of the Imperial series, are restricted in extent and represent modifications of other types. The very fine sandy loam, which occurs in a number of small bodies along the Alamo and New rivers, has a surface soil containing a high proportion of silt. Under virgin conditions this fine material commonly occurs as one or more thin strata of compact silt loam. Under cultivation, the surface soil is mixed and stratification is destroyed. The loam also occurs as small bodies in the same locality, and locally it has acquired a thin surface deposit of silt or clay largely as a result of irrigation. The remaining three types — silty clay loam, silty clay, and clay — constitute nearly 24 per cent of the total area surveyed. Each type is represented by several large bodies along or near the two river channels, where they appear to be alluvial or lacustrine deposits upon wind-modified subsoil material. These three types are characterized by relatively compact and impervious surface soils and surficially are indistinguishable from comparable members of the Imperial series. The Rositas Series. — The soils of the Rositas series consist of 6 feet or more of a light brownish gray to light grayish brown, loose, pervious, coarse-textured material. As in the case of the preceding three series, the surface soil and subsoil are uniformly calcareous and have little organic matter. The surface soils are identical with those of the Melo- land series, while the subsoils are essentially the same as those of the Holtville. Owing to their loose and friable character, the Rositas soils are readily modified by winds and many of the virgin bodies are marked by hummocks and even by low dunes. Five types of the Rositas series — the gravelly fine sand, sand, fine sand, very fine sand, and very fine sandy loam — were mapped. They comprise slightly more than 8 per cent of the total area surveyed. The first three types occur principally along the eastern and western Cm. 334] Soils and Crops of Imperial Valley 15 margins of the Valley where they are associated with extensive bodies of dunesand and of Superstition soils. The gravelly fine sand is of small extent and is nontypical of the series. It appears to have had its origin in material derived from the old sedimentary deposits of the higher desert slopes to the east. The type has been subject to such severe wind erosion that most of the bodies are characterized by a "desert pave- ment," or surface layer of gravel. The sand and fine sand members of TABLE 3 Eelation Between - Surface and Subsoil Textures in the Imperial, Holtville, Meloland, and Rositas Series as Indicated by the Acreage Distribution of the Soil Types Texture of surface soil Series with impervious fine-textured subsoils Series with pervious coarse-textured subsoils Imperial Meloland Holtville Rositas Gravelly sand, gravelly fine sand, and sand .... acres acres 4,096 75,200 acres acres 6,016 41,856 6,720 29,312 210,624 14,848 41,536 128,128 9,792 the series closely approximate dunesand, the principal basis for separa- tion being the more regular and more nearly level relief of the Rositas soils. The very fine sand and very fine sandy loam have surface soils of somewhat finer texture than the others and contain an admixture of small amounts of silt and clay. Consequently, they have a smoother and less hummocky surface than the coarser members of the series. The sub- soils vary to some extent. In certain localities they consist of incoherent sand, fine sand, or sandy loam, while in others a definite stratification occurs and indicates that a part, at least, of the Rositas material is water-laid. Relationship Between Four Series of Soils. — From the standpoint of profile development, the Imperial, Meloland, Holtville, and Rositas series are decidedly youthful soils without any evidence of weathering. Although they are calcareous, there is no definite segregation or con- centration of lime within any particular zone. Except for textural varia- tions, resulting from the vagaries of depositing agencies, the surface soils and subsoils of all four series are notably alike. In the absence of other recognized criteria at the time of the surveys, these four series were differentiated on the basis of the character and sequential arrange- ment of the textural variations. The degree to which these textural differences are involved in the differentiation of the series is suggested by data presented in table 3. Fig. 3. — Subsoil conditions in Imperial Valley. Soils having dense, fine-textured subsoils are shown in solid black ; soils having pervious, coarse to medium-textured subsoils are represented by oblique lines. See figure 1 for names of cities and towns indicated by the circles. Cir. 334] Soils and Crops of Imperial Valley 17 This table clearly shows the degree to which the textures of both sur- face and subsoil were used for differentiating the series. While some question might be raised as to the pedologic justification for the separa- tion, these textural differences are nevertheless of great agronomic significance. The soils of the Valley — excluding the bordering mesa lands and some material that has been washed in from them — are all of like origin, coming from the sediments of the Colorado River. As earlier explained, they differ on the basis of mode of deposition, most of the fine-textured materials being lake deposits, while the coarser-textured materials have been rearranged and modified by wave action, stream flow, or by wind. On the basis of origin and mode of formation, factors which are of greatest importance in the case of young, unweathered soils, the soils of the Valley are very similar. Drainage conditions markedly affect the character of weathering and the relation of soil to plants. The effect of different conditions of drainage are not only appar- ent in the older soils, but are of great importance in young soils also. The dense clay subsoils of the Imperial and Meloland series markedly retard the downward movement of water, and under the artificial con- ditions of irrigation may produce poor drainage ; whereas the coarser- textured, more pervious subsoils of the Holtville and Rositas favor con- tinuing good drainage conditions. On the basis of these conditions, the separation of the soils into the two groups of series is fully warranted, particularly when the associated agronomic aspects are considered. Figure 3 shows the distribution of the soils in the Valley on the basis of the subsoil conditions. The separation of the Meloland from the Imperial, and the Rositas from the Holtville, on the agronomic or agricultural basis is important and is recognized generally by the farmers of the Valley. All of the lands of the Meloland and Rositas series are termed "soft" soils, this term referring to their sandy texture and the ease with which they can be worked into a good condition of tilth. The fine-textured soils, all of which are in the Imperial and Holtville series are termed "hard" soils, referring to the firm consistence of the surface soil and the difficulty of working them into good tilth. "Medium" soils include the silty soils of the Imperial and Holtville series. Figure 4 shows the distribution of the fine-textured and coarse-textured surface soils in the Valley, or the "hard" and "soft" soils. Drainage and Alkali. — In the preceding discussion reference has repeatedly been made to conditions of poor drainage. These conditions are due to the occurrence of the relatively impervious, fine-textured, lacustrine strata in the deeper subsoil or substratum. The actual ground water table in the Valley is very deep, and conditions of poor drainage Fig. 4. — Surface soil conditions in Imperial Valley. The fine-textured surface soils of the Imperial and Holtville series, locally known as "hard" and "medium" lands, are shown in solid black ; the coarse and medium-textured surface soils of the Melo- land and Rositas series, locally known as "soft" lands, are represented by oblique lines. See figure 1 for names of cities and towns indicated by the circles. Cm. 334] Soils and Crops of Imperial Valley 19 comparable to those in most regions do not exist except in the extreme northern part adjacent to the Salton Sea. Poor drainage conditions in the Imperial and Meloland series are due to accumulations of water above the dense clay subsoils, essentially a very shallow "perched" water TABLE 4 Extent to Which Each Soil Type Is Affected With Alkali* Soil type Acreage free from alkali Acreage slightly affected Acreage moderately and strongly affected Total of soil type Total acreage affected with alkali Per cent of total acreage affected with alkali Imperial clay Imperial silty clay Imperial silty clay loam Imperial clay loam Imperial loam Imperial very fine sandy loam Subtotal, Imperial series Holtville clay Holtville silty clay Holtville silty clay loam Holtville loam Holtville very fine sandy loam Subtotal, Holtville series Meloland fine sandy loam Meloland fine sand Meloland gravelly sand Subtotal, Meloland series Rositas very fine sandy loam.. Rositas very fine sand Rositas fine sand Rositas sand Rositas gravelly fine sand Subtotal, Rositas series Dunesand 1,625.6 2,787.6 3,634.6 13.0 482.0 203 1,278.8 6,673.0 11,682.2 1,826.0 6,340.2 19,302.0 13,475.4 3,980.0 4,641.0 9,158.0 22,044.6 2,457.6 1,472.0 15,991.2 8,513.8 34,189.8 10,710.8 2,797.0 1,794.0 44.0 14,119.2 30,579.2 16,994.8 1,617.0 19,000.8 4,978.2 6.4 1,033.0 4,787.2 1,087.6 1,510.4 0.0 632.6 65,636.6 70,031.4 5,430.6 6,726.0 2,268.0 1,929.0 30,746.0 44,731.8 12,849.0 1,805.0 1,471.2 16,161.2 2,218.4 4,118.0 3,078.4 1,699.8 576.0 0.0 75,776.0 107,008.0 19,776.0 9,536.0 4,544.0 2,176.0 218,816.0 46,144.0 81,984.0 41,526.0 5,248 9,600.0 184,602.0 54,464.0 20,672 4,095.2 79,231.2 9,792. 17,024. 24,832. 4,544 1,472 67,664. 400. 17,024.0 74,150.4 104,221.2 16,141.4 9,523.0 4,062.0 1,973.0 210,071.0 44,865.2 75,311.0 29,843.8 3,422.0 3,259.8 166,701.8 35,162.0 7,196.5 115.2 42,473.8 5,151.0 7,865.6 2,787.4 2,086.4 0.0 17,890.4 1,032.8 97.85 97.20 81.62 99.89 89.50 90 75 96.89 97.22 91.86 71.89 65.40 33.95 84.86 64.59 34.75 2.81 63.53 52 60 46.20 11.22 45.98 31.02 * As shown by Soil Surveys of El Centro (1918) and Brawley (1920) Areas. Some of the acreage affected has been decreased by drainage and reclamation. table. Where poor drainage exists in the Holtville and Rositas soils, it is due to the existence below the soil and subsoil (normally considered as about 6 feet) of dense and relatively impervious clay layers. The water table is perched on these clay layers, and if drainage outlets are provided by deep ditches lateral flow above the impervious layer relieves the conditions of poor drainage. Closely associated with the movement of water through these several types of soil is the occurrence of alkali. Where the downward movement of soil moisture is impeded, surface evaporation normally results in the 20 University of California — Experiment Station accumulation of soluble salts. Reflecting this circumstance, and also possibly evidencing further the lacustrine origin of the material, the Imperial series of soils is marked by relatively high concentrations of alkali. In contrast, the Rositas series is characteristically free from in- jurious concentrations. The Holtville soils are somewhat less affected than the Imperial probably due to a better subdrainage ; while the Melo- land series (particularly where perched water tables have occurred through either lateral seepage or excessive irrigation) exhibits more damage than the soils of the Rositas series. The degree to which the soils of each of these four series are affected with alkali is indicated in table 4. The term "alkali" covers a condition of the soil where there is present a sufficient accumulation of soluble salts to cause injury to plants. These may be neutral salts, such as sodium chloride (common salt), or sodium sulfate (Glauber's salts) which properly should be called salines; or they may be made up in part of sodium carbonate (washing soda) which is a true alkali. Although both types of salts are present to some degree in the soils of the Imperial Valley, the salines dominate, there being extremely small amounts of the true alkali. All of the soils of the Imperial Valley naturally contain large quan- tities of soluble material. They have never been leached by rain waters. They have been wetted and leached only by the waters of the Colorado River, and of the lake that has from time to time occupied the valley. As these waters evaporated, their content of soluble materials was left in the soil. Since the introduction of irrigation, conditions have changed. Porous soils are being leached, while soils having dense clay subsoils or substrata horizons have developed conditions of poor drainage. Wherever poor drainage occurs with a water table within the distance of ordinary capillary rise to the surface, soluble materials in the soil mass will tend to move upward and accumulate in or on the surface soils. Wherever such poor drainage exists, there is danger of accumulations of soluble salts or "alkali." Reclamation of lands after alkali has accumu- lated involves special operations with consequent expense, and it is much wiser to maintain conditions of good drainage and thereby prevent alkali accumulations. The removal of alkali accumulations may be accomplished in many instances by the provision of adequate drainage followed by a thorough leaching of the soil mass. Sufficient water must pass through the soil to dissolve the salts present and carry them down and out of the soil mass into the regional drainage. This may be difficult or easy, according to the physical and chemical characteristics of the soil and the alkali materials present. Cm. 334] Soils and Crops of Imperial Valley 21 In the Imperial Valley the essentials for successful reclamation are free and adequate drainage and sufficiently prolonged leaching to dis- solve and remove the salts. Fine clays may be naturally so dense and impervious as to make reclamation an economic impossibility, while on soil of less extreme character special treatments might be effective. Porous soils are most readily leached and usually are easiest to reclaim. The soils of the Rositas series with their coarse textures and perme- able conditions of both surface and subsoil have the smallest area in- jured by alkali, as shown by table 4, and can be protected from alkali accumulation provided good drainage is maintained. For this series in particular reclamation of the alkali-affected areas should not be difficult. These conditions also apply to the coarse and medium-textured Holt- ville soils, while the Holtville silty clay and clay not only have a larger area affected by alkali accumulations, but are more difficult to reclaim because of the fine texture of the surface soils and the slow rate at which water penetrates them. The coarse-textured subsoils of the Holtville series make the provision of subdrainage readily possible, and further alkali accumulation can be prevented. The Meloland series has fine- textured and rather dense subsoils, but practically all of the types present in the Valley have coarse-textured surface soils. The provision of adequate drainage is difficult and not infrequently calls for the in- stallation of tile drains in addition to the main drainage ditches in order to make possible carrying away of water from the upper portion of the subsoil. If provision for lateral movement of water through tile drains is adequate, it is readily possible to prevent any further accumu- lation of alkali and, if properly handled, to reclaim the soils of the Meloland series that now have alkali accumulations. The soils of the Imperial series as a normal condition have large amounts of alkali present, over 80 per cent having moderate to strong accumulations. The dense character of the subsoil makes almost impossible any down- ward leaching, and as most of the surface soils are medium to fine- textured, the percolation of water through them is slow. The very fine sandy loam and loam may be reclaimed by following the provision sug- gested for the Meloland soils. The same methods may prove successful with the clay loam and silty clay loam although the process will be much slower and more difficult. It is exceedingly difficult to provide drainage for the silty clay and clay that would permit of sufficient leaching to remove the salts from these soils. Flooding, with what leaching could be accomplished, may improve the conditions to some extent; but the re- moval of the salts from the soil mass will be exceedingly slow and prob- ably not economically feasible. 22 University of California — Experiment Station THREE DECADES OF AGRICULTURAL DEVELOPMENT Until the beginning of the present century the north slope of the delta fan remained a poorly denned and undeveloped portion of the Colorado Desert. Though the agricultural possibilities of the area had been com- YEAR: ACREAGE UNDER IRRIGATION: 100,000 200,000 300,000 1-00,000 Fig. 5. -Increase in irrigated acreage by years, 1901 to 1930, inclusive. mented upon favorably by several explorers during the preceding half century, it was not until June, 1901, that a canal was constructed and the first water brought in for irrigation purposes. With the diversion of this water supply from the Colorado River and the necessity of attract- Cm. 334] Soils and Crops of Imperial Valley 23 ing many settlers for its utilization, the promoters of the enterprise decided to avoid the use of such ominous terms as "Salton Sink" and "Desert," and originated the name "Imperial Valley" to designate lands which they proposed to irrigate. 1903: 1909: i9ia 1927: 1930: (ESTIMATED) (U.S. CENSUS, COUNTY} (US.CENSUS, COUNTY) (IMP. IRR.DIST. REFT.) (IMP irr. dist. rept.) TOTAL AR£A CULTIVATCO- ^mes.ooo ■ \I90,7II 4IS.304 MV ' JF WM389,048 H V "-'<■ 4 J* £60 WH£A7& BARtCr- WksOM3 HI * Hi 43,336 1 Wm I -5 o> d ® g !> ° ■as, S§ ~§ o 5 O CD Ph d 2^ O rO GQ O 2 ►» d ed d rt eg d O H o 3 «3 ^ dri4 l-H 3 cs I* S^ d^3 o o bed «H B O p ® 2 g 00 b/) as bJD d o too 26 University of California — Experiment Station Five Major Types of Agriculture. — The complexity of the agricul- tural structure makes difficult any attempt to classify the diverse, and in some cases interdependent, farming activities. In a general way, they may be grouped in five major classes, as follows : Forage Production. — Alfalfa farming, which utilizes about half of the cultivated acreage, is the keystone of local agriculture. Not only is it necessary for the livestock activities of the Valley, but the successful production of several other more remunerative crops also is traceable, in part, to its beneficial effects on the soil. Barley has proved to be one of the more profitable crops on many of the fine-textured, alkali-affected soils of the Valley. It occupies an acreage second only to that of alfalfa, and is significant in the production of hay and forage. Bermuda grass thrives in hot weather, is extremely tolerant of alkali, and withstands heavy pasturage. Bermuda pastures are maintained for the summer feeding of livestock. Figure 8 shows the distribution of alfalfa and barley in the Valley. Truck Farming. — The production of cantaloupes is the outstanding truck-farming activity in the Imperial Valley. Half of the United States shipments of cantaloupes originate here. In June alone, approxi- mately 10,000 cars of cantaloupes are shipped out. With intensive cul- tural practices, selected strains of seed, and the use of the coarser- textured and warmer soil types, the problems of production have been largely solved. A critical marketing problem, that of shipping large quantities of melons in a short space of time without unduly lowering prices, still confronts the growers. The production of lettuce, charac- terized by a similar marketing problem, has been of importance for only a few years. As both cantaloupes and lettuce are grown by large organ- izations which generally lease (for a three-year period) farms which have been in alfalfa for a number of years, they have been grown for the most part on approximately the same range of soils. This practice of leasing alfalfa farms has been a serious handicap to alfalfa farmers and to dairymen, as they in turn are forced periodically to seek new farms for their operations. The distribution of cantaloupes and lettuce in the Valley is shown in figure 8. Orchardry and Yineyardry. — Orchards of grapefruit, the only tree crop of importance in the Valley, occupy about 9,000 acres. Nearly two- thirds of this acreage is in bearing trees, with the older plantings con- sisting of numerous small acreages on nearly all types of soil. Early table grapes have been grown for several years and although the acreage is not great, this activity has been an important form of land use. Cotton and Grain- Sorghum Production. — Probably none of the major agricultural activities of Imperial Valley have experienced greater Cir. :i34 Soils and Crops of Imperial Valley 27 Fig. 8. — Crop distribution February 1, 1927. Each dot represents 80 acres, and, where practicable, is located on the map within the section in which it occurs. 28 University of California — Experiment Station vicissitudes than cotton farming. Cotton was grown here commercially for the first time about 1912, and large yields on the well-suited, medium- textured soils, together with profitable prices, caused a rapid expansion in acreage. In 1920, with nearly 100,000 acres planted to cotton, the re- turns were well below the cost of production. Since that disastrous season, in which many farmers were ruined, the acreage devoted to cotton has fluctuated markedly from year to year. Approximately 2,500 acres were planted to cotton in 1933. Grain sorghums are excellently suited to the conditions. They are tolerant of alkali and they withstand the high summer temperatures. For these reasons, grain sorghums, and particularly milo, are the only seasonal crops grown to any notable extent during the summer months. The 25,000 acres planted to grain sorghums in 1930 were scattered throughout the entire Valley, an indication of the general popularity of this summer grain which can be planted on lands that may have been used during the winter and spring for barley or other crop. Dairying and Other Livestock Activities. — Dairying is the only live- stock activity that is conducted with similar intensity in all seasons of the year. Nearly all of the dairy cows are in commercial herds and most of these are in the southern, more highly developed, part of the Valley. This localization of dairy stock is in interesting contrast to that of beef cattle, most of which are in the northern, more recently settled portion. In addition to a large and more or less permanent population of live- stock and poultry, maintained almost exclusively on locally grown products, there are thousands of beef cattle and sheep which are brought to this section from the open range to be "finished" on the winter pas- turage of alfalfa and barley, and on cotton and grain sorghum plantings from which the crop has been harvested. The cattle are commonly shipped on to market in early spring, usually before the grass-finished stock from other localities is ready for marketing. The sheep industry has two phases : ( 1 ) lambs are imported in the autumn and fattened to be marketed in the spring, and (2) ewes are brought into the Valley in autumn, and bred. The following spring the older ewes are marketed along with the spring-born lambs. The swine industry also has a definite relation to the winter pasturage; autumn-born pigs (from breeding stock which remains in the Valley throughout the year) are carried through the winter to be marketed as feeder stock before the advent of hot weather, and feeders are autumn-imported and finished during the winter. According to the last census, the livestock population of the Valley included 18,320 dairy cows, 42,519 head of other cattle, 36,893 sheep, 25,585 hogs, 5,057 horses, and 1,898 mules. In addition there were 16,588 dozen chickens and 17,383 dozen turkeys. Cir. 334] Soils and Crops of Imperial Valley 29 The magnitude of the livestock industry greatly enhances the value of many of the field crops grown. Great quantities of grain, hay, ensilage, and pasture plants are consumed locally by livestock. A great amount of the cotton by-products, such as cottonseed cake, meal, and hulls, are fed to the local beef cattle. Thus field-crop production and the animal industries are very closely allied, and are interdependent one upon the other. They form the foundation of a durable agriculture in this region, which no doubt will grow rather than diminish in importance and value in future years. Distinct advantages are enjoyed by the livestock and poultry indus- tries in the Valley. Green feed is produced every month in the year. The cost of adequate housing is far less than that required in agricultural sections having rigorous winters. The great markets of Los Angeles are easily and quickly reached. The great quantities of feed produced here, the mild winter climate, the accessibility of markets, are contributing factors to a most economical feeding and marketing of livestock — ad- vantages which apply alike to all branches of the livestock and poultry industries. Present Agricultural Trends. — After three decades of pioneer expansion, the agriculture of the Valley appears to have entered upon a period of stabilization. That such a development is now underway is suggested by changes now occurring in the general structure of the local agriculture. During earlier years the farmers apparently were interested in short- time occupancy of the land. They planned to secure as quickly as pos- sible the hoped-for profits of their toil, and then depart for other lo- calities. In recent years their attitude has changed more or less, and some of them, notably the orchardists, have entered upon definite long- term programs. Truck farmers also are beginning to adopt similar pro- grams, which offers the alfalfa growers an opportunity to do likewise. 16 Another change involves the tenure of land. In 1925, 66 per cent of the farms were operated by tenants; in 1926, 63 per cent. In 1930, the latest year for which data are available, 62 per cent were operated by tenants and 38 per cent by owners. Although the peculiar system of leasing alternately to truck farmers and to alfalfa growers has con- tributed largely to this situation, another and probably equally signifi- cant influence has been the low sale value of Valley land relative to ren- 16 Growers of alfalfa have recognized for years the disadvantages of a system which involves the periodic transfer of their operations to new locations, but have been unable to withstand the demand of truck crop producers for alfalfa land. That this disturbing demand for land will be lessened in the future is indicated by several purchases of land by the truck-farming organizations within the last three or four years. 30 University of California — Experiment Station tal value. The scale of rents is not uhprofitably high when compared with crop returns in favorable years. The relatively low sale value of land is traceable, at least in part, to a widespread unwillingness on the part of farmers to assume the respon- sibilities of land ownership in the Valley. Much of this unwillingness is due, in turn, to a general fear of property destruction through another disastrous overflow of the Colorado Kiver. The elimination of this haz- ard with the completion of Boulder Dam and other flood control works along the river will make land ownership more attractive and tenancy may be expected to further decrease in the future. CROP DISTRIBUTION IN RELATION TO SOIL TYPE In order to determine the distribution of crops and the extent to which the different soil types were utilized for crops, a detailed field survey of land use was made during March and April, 1927. The unique character of the agriculture involving double cropping of some of the land without the usual seasonal planting and harvesting periods, made this survey especially difficult. Early spring is the most- favorable time for making the observations, for most of the important annual crops are growing during the winter and spring months, and at that time there is usually some evidence of the previous crop, even though the field be plowed and ready for planting a new crop. Rapid work is necessary in order to cover an adequate area, yet not continue into another cropping season. Land that was in lettuce during the winter might be seeded to sorghum, or land that was in barley or alfalfa might be plowed up for cantaloupes ; hence to be an accurate picture of the use of the land at any season, the whole area studied must be mapped in the briefest possible time. This survey covered only the southern, more highly developed por- tion, although at the outset it had been hoped that the entire Valley might be included. A procedure used successfully in an earlier study of soil utilization 17 was employed in making this survey; all plantings of crops were identified, measured, and plotted on a suitable base map, which was then superposed on a map of the soils 18 and a combined crop- soil map constructed. The individual acreages of each crop on each type of soil were next measured and the results tabulated (table 5) . The survey covered 238,603.5 acres, exclusive of roads and other rights of way. It included 6,520.5 acres within the limits of the six urban 17 Cosby, Stanley W. Utilization of the soils in the Gilroy region. Hilgardia 1 (18) :455-478. 1926. is Map accompanying Soil Survey of the El Centro Area. Cm. 334] Soils and Crops of Imperial Valley 31 communities and 13,274.0 acres of rough, eroded lands associated with the tributaries and gorge-like channels of the New and Alamo rivers. Of the remaining 218,809.0 acres available for crop production, 47,186.5 acres were uncultivated, although plant remains and other evidence indicate that at least 10,595.0 acres, or more than one-fifth of the uncul- tivated acreage, had been planted previously to crops. A total of 171,061.0 acres of rural land was used for crop produc- tion. 19 Of this total, 717.5 acres comprised plantings of cotton and grain sorghums made during the preceding season, 19,071.0 acres consisted of lands which were plowed or otherwise being prepared for planting, and 151,273.5 acres were occupied by crops in various stages of growth (fig. 7). Crop- Soil Measurements. — The crop-soil measurements show marked variations in acreage between the several crops and between the several soils. In the area covered by this crop survey, alfalfa occupied 93,098.0 acres, or more than one-half of the rural land used for crop production, while date palms were planted on only 93.0 acres. Holtville silty clay, with a total of 41,465.0 acres, is the most extensive of the eighteen types of soil; and Carrizo sand, with only 26.0 acres, is the least extensive. The measurements also demonstrate that all of the soil types are not used to a like extent for crop production. On an acreage basis, Holtville silty clay (with 33,455.0 acres or 84.78 per cent of the rural area of this soil used for crops) ranked first and was followed, in order of descend- ing acreages, by Imperial silty clay (28,987.5 acres or 86.53 per cent) ; Meloland fine sandy loam (28,149.5 acres or 87.63 per cent) ; Holtville silty claj 7 " loam (25,203.5 acres or 85.64 per cent) ; Imperial silty clay loam (14,210.5 acres or 86.52 per cent) ; Holtville clay (11,646.5 acres or 68.92 per cent) ; Rositas very fine sand (11,285.5 acres or 80.02 per cent) ; Imperial clay (9,863.0 acres or 63.63 per cent). The ten remain- ing types were planted to even a lesser extent. Likewise, these measurements demonstrate that none of the more im- portant crops was planted to a like degree on the several types of soil. More than one-third of the total acreage of alfalfa was planted on two of the medium to fine-textured soil types, Holtville silty clay (18,603.5 acres) and Imperial silty clay (16,701.5 acres). One-fifth of the melon acreage 20 was on the medium to coarse-textured Meloland fine sandy loam, while a slightly larger proportion of the lettuce acreage was on the medium to fine-textured Holtville silty clay loam. i9 More than one-third (2,430.0 acres) of the aggregate area of the urban com- munities also is planted to crops. 20 About 80 per cent of this acreage consists of plantings of cantaloupes ; the re- mainder is made up of watermelons, Persian melons, and others of this group. 32 University of California — Experiment Station TABLE 5 Acreage of Each Crop on Each Soil Type in Crop, or Type of Land Use Alfalfa Acreage of the crop on the soil type Per cent of total acreage of the crop Per cent of total acreage of the soil type.. Barley, Wheat, and Oats Acreage of the crop on the soil type Per cent of total acreage of these crops.,... Per cent of total acreage of the soil type.. Bermuda Grass Acreage of the crop on the soil type Per cent of total acreage of the crop Per cent of total acreage of the soil type. All Forage, Hay, and Grain Acreage of these crops on the soil type Per cent of total acreage of these crops Per cent of total acreage of the soil type. Cotton Acreage of the crop on the soil type Per cent of total acreage of the crop Per cent of total acreage of the soil type. Grain Sorghum Acreage of the crop on the soil type Per cent of total acreage of the crop Per cent of total acreage of the soil type Lettuce Acreage of the crop on the soil type Per cent of total acreage of the crop Per cent of total acreage of the soil type Melons Acreage of the crop on the soil type Per cent of total acreage of the crop Per cent of total acreage of the soil type.. Tomatoes Acreage of the crop on the soil type Per cent of total acreage of the crop Per cent of total acreage of the soil type. Green Peas Acreage of the crop on the soil type Per cent of total acreage of the crop Per cent of total acreage of the soil type. Imperial Clay holtville Clay ,097.0 6.46 39.33 1,026.5 17.21 6.61 189.0 1.81 1 22 7,312.5 6.6S 47. ie 155.0 11.23 1.00 302 7.28 1.95 108.0 1.31 0.70 503.5 2.83 3.25 20.0 1.79 0.13 15.0 7.65 0.10 Imperial Silty Clay 7,617.0 ' 8.24 45.06 838.0 14.08 4.96 372 3.56 2.20 ,827.0 52.22 230.5 16.71 1.36 424 10.23 2.51 238.0 2.88 1.41 647.0 3.63 3.83 38.5 3.43 0.23 0.03 ,710 5 17.97 49.89 913.0 15.34 2.73 1,672.0 15.97 4.99 19,295 5 17.63 57.61 [69.5 12.28 0.51 590.5 14.26 1.76 1,729.0 20.89 5.16 1,910.0 10.74 5.71 93.5 8.32 0.28 1.5 0.76 holtville Silty Clay 18,603.5 20.00 46.99 1,097.5 18.41 2.78 1,859.5 17.76 4.68 21,560.5 19.67 54.45 170.5 12.32 0.43 723.5 17.43 1.83 1,536.5 18.56 3,351.0 18.86 8.47 171.0 15.22 0.43 51.0 26.01 0.13 Imperial Silty Clay Loam * Includes 19.0 acres of alfalfa on Meloland gravelly sand and 5.5 acres of alfalfa on Carrizo sand. Cm. 334] Soils and Crops of Imperial Valley 33 the El Centro Soil Survey Area; Spring, 1927 Holtville Silty Clay Loam Holtville Very Fine Sandy Loam Meloland Fine Sandy Loam Rositas Very Fine Sand Melo- land Fine Sand Rositas Fine Sand Rositas Sand Dune- sand Super- stition Gravelly Sand Total Acreage of Crop, or of Land Use 12,851.5 1,382.0 14,008 5 5,610.5 420 5 1,295.5 275 5 454.0 80.0 93,098.0* 13.83 1 48 15 06 6.02 0.42 1.39 0.29 0.49 0.09 100.00 43 65 30.13 43.60 39.79 20.47 24.58 12.68 8.36 10.68 42.56 428 23 5 1,001.0 16.82 3.12 266.0 38.0 62.5 13.0 5,956 7.19 0.39 0.51 4.47 1.89 0.64 1.84 1 05 1.19 0.22 0.61 100.00 1.45 2.72 1,233.5 499 2,106.0 1,007.0 70.5 284.0 13 208.5 23.5 10,471.5f 11.78 4.77 20.12 9.62 0.67 2.70 0.12 1.99 0.22 100.00 4.19 10.87 6.56 7,14 3.42 5.38 0.61 3.84 3.13 4.78 14,513.0 1,904.5 17,115.5 6,883.5 529.0 1,642.0 301.5 662.5 103.5 109,525.5*t 13.25 1.74 15.64 6.29 0.48 1.50 0.27 0.60 0.09 100.00 49.30 41.51 53.28 48.82 25.73 31.15 13.90 12.20 13 81 50.06 200.0 161.5 100.0 29.0 2.0 1,380.5 14.49 11.70 7.25 2.10 0.14 100.00 0.68 0.50 0.71 1.43 0.04 0.63 800.0 67.5 651.0 172.0 36.5 55.5 11.0 6.0 18.0 4,145.0 19.33 1.63 15.71 4.15 0.88 1.34 0.27 0.14 43 100.00 2.72 1.47 2.03 1.22 1.77 1.05 0.51 0.11 2.40 1.89 1,860.0 74.5 0.90 1.62 1,234.0 14.92 3.84 503.5 6.09 3.57 184.5 2.22 8.97 80 0.97 1.52 37.0 0.45 0.68 8,273.5 22.49 100.00 6.32 3.78 3,407.5 619.5 3,502.0 1,260.5 225.0 266.5 285.0 139.5 17,786.0 19.17 3.48 13.51 11.0 0.98 0.24 19.71 10.90 254.5 22.63 0.79 7.08 8.93 172.0 15.30 1.22 1.26 10.94 18.0 1.60 0.88 1.48 5.05 1.60 13.16 3.0 0.27 0.14 0.78 2 59 10.5 0.93 0.19 100.00 11.58 8.13 256.0 1,128.0 22.41 100.00 0.87 0.51 16.5 5.0 2.55 0.10 50.5 25.78 0.16 10.5 5.36 0.07 3.0 1.53 0.15 196.0 8.42 100.00 0.06 0.09 t Includes 3.5 acres of Bermuda grass on Superstition fin< sand. (Table 5 continued on page 34) 34 University of California — Experiment Station TABLE 5— Crop, or Type of Land Use Other Truck Crops Acreage of these crops on the soil type Per cent of total acreage of these crops Per cent of total acreage of the soil type . All Truck Crops Acreage of these crops on the soil type Per cent of total acreage of these crops Per cent of total acreage of the soil type . Asparagus Acreage of the crop on the soil type Per cent of total acreage of the crop Per cent of total acreage of the soil type.. Grapefruit Acreage of the crop on the soil type Per cent of total acreage of the crop Per cent of total acreage of the soil type Grapes Acreage of the crop on the soil type Per cent of total acreage of the crop Per cent of total acreage of the soil type Dates Acreage of the crop on the soil type Per cent of total acreage of the crop Per cent of total acreage of the soil type . Strawberries Acreage of the crop on the soil type Per cent of total acreage of the crop Per cent of total acreage of the soil type.. Other Perennial Crops Acreage of these crops on the soil type Per cent of total acreage of the crops Per cent of total acreage of the soil types All Perennial Crops Acreage of these crops on the soil type Per cent of total acreage of these crops Per cent of total acreage of the soil type.. Plowed Land Acreage of plowed land on the soil type... Per cent of total acreage of plowed land.. Per cent of total acreage of the soil type.. Imperial Clay 3.0 1.55 0.02 19 5 2 36 4.20 12.5 1.55 0.08 195.0 4.38 1.26 30.00 80 0.19 4.0 3.74 03 241.5 2.58 1.56 183.5 6.20 7.64 holtville Clay 5.5 2 85 03 935 3 39 5.53 3.0 37 02 142.0 3.19 0.84 20.0 0.53 0.12 5.0 5.38 0.03 170.0 1.01 1,044.0 5.48 6.18 Imperial Silty Clay 15.0 7.77 04 3,749 13.59 11.19 89.0 11.05 0.27 948.5 21.32 2.82 674.5 17.96 2.01 26.0 27.96 08 3.0 2.79 01 13.5 8.87 0.03 1,754.5 18.75 5.24 3,366.5 17.66 10.05 holtville Silty Clay 39.5 20.46 0.10 5,149.0 18.67 13.01 122.5 15.19 0.31 806.5 18.13 2.04 1,026.0 27.29 2.59 16.0 17.21 0.04 40.0 26.22 0.10 2,011 21.47 5.08 3,840.5 20.15 9.70 Imperial Silty Clay Loam Cm. 334] Soils and Crops of Imperial Valley 35 (Continued) Holtville Silty Clay Loam Holtville Very Fine Sandy Loam Meloland Fine Sandy Loam ROSITAS Very Fine Sand Melo- land Fine Sand ROSITAS Fine Sand ROSITAS Sand Dune- sand Super- stition Gravelly Sand Total Acreage of Crop, or op Land Use 44.5 9.0 4.66 20 719.0 2.61 15.67 3.0 0.37 06 29.5 0.66 0.64 61.0 168 1.34 2.5 1 30 45.0 23.33 0.32 1,991.5 7.25 14.11 42.0 5.21 0.30 297.5 6.69 2.11 324.0 8.72 2 30 4.5 4.84 03 3.5 3.24 0.02 0.5 0.33 5.5 2.85 0.10 352.0 1.28 6.67 26.5 3.29 0.50 49.5 1.11 0.94 48.5 1 29 0.92 193.0 23.04 100 00 0.15 09 5,584 5 5,043.5 18.27 15.70 302.0 37 47 0.94 817.0 18.37 2.55 673.0 17.91 2 10 25.0 26.89 0.08 14 12.95 0.04 20.0 13.16 0.06 1,851.0 19.79 5.77 3,213.5 16.85 10.00 430.5 1.56 20.94 288.0 1.04 13.30 28.5 3.54 1.32 8.0 0.18 37 17.0 45 78 187.0 0.68 3.46 5.0 0.62 0.09 40.5 91 75 39 5 1 05 0.73 27,576.5 20.23 100.00 18.98 12 60 132.0 806 16.38 100.00 0.45 37 615.5 32.0 0.72 1 55 4,450.0 13.82 100.00 2.09 2.03 598 3,753.5 15.93 100.00 2 03 1.72 12 93.0 12.90 100 00 0.04 04 55.5 108.0 51.35 100 00 0.19 05 35.0 7.5 4.93 0.16 101.0 1.08 2.20 167.5 0.88 3.65 152.0 23.03 100.00 12 0.07 1,448.0 672.0 7.18 4.76 1,434 5 7.51 10.17 32.0 0.34 1.55 220.0 1.15 10.70 124 5 1.33 2.36 288.5 1.51 5.48 53.5 54 2.47 98.5 0.52 4.55 85.0 0.91 1.57 115 5 0.61 2.13 9,362.5 15.45 100.00 4.92 4.28 2,503.5 13.12 8.51 42.5 0.22 5.67 19,071.0 100.00 8.72 (Table 5 concluded on page 36) 36 University of California — Experiment Station TABLE 5— Crop, or Type of Land Use Imperial Clay holtville Clay Imperial Silty Clay Holtville Silty Clay Imperial Silty Clay Loam Miscellaneous Use Acreage of this use on the soil type 39.0 27.57 0.10 8.0 16.50 0.02 64.0 17.22 0.16 33,566.0 19.55 84.78 6,028.0 12.78 15.22 39,594.0 18.11 100 00 10 Per cent of total acreage of this use 7 07 Per cent of total acreage of the soil type 06 Eucalyptus Trees Acreage of eucalyptus trees on the soil type 3 5 Per cent of the total acreage of eucalyptus 7.22 Per cent of total acreage of the soil type 02 Farmstead Lots Acreage of farmstead lots on the soil type 19.0 5.12 0.12 9,863.0 5.75 63.63 5,638 11.96 36.37 15,501.0 7.09 100.00 16.0 4.31 0.11 11,646.5 6.78 68.92 5,252.5 11.14 31 08 16,899.0 7.63 100.00 62.0 16.69 0.17 28,987.5 16.89 86.53 4,511.5 9.56 13.47 33,499.0 15.33 100.00 31 Per cent of total acreage of farmstead lots 8 34 0.19 Total Used Land Acreage of used land on the soil type 14,210.5 8.28 86 52 Total Unused Land 2,216.5 4.70 13.48 Total Rural Land 16,427.0 Per cent of total acreage of rural land 7.52 Per cent of total acreage of the soil type 100.00 Total rural and urban land 16,083.0 17,644.0 35,221.5 41,465.0 16,706.5 X Includes 871.5 acres of unused land on Rositas very fine sandy loam; 26.0 acres of unused land on Meloland However, even a casual inspection of the detailed data relating to the acreages of each crop on each type of soil (table 5) reveals that more than a mere comparison of acreages is necessary if the full import of the crop distribution is to be shown. Expressing the distribution of the crops as a percentage of the total acreage of each soil type involved, gives a more informative series of values. For example, grain occupied 6.61 per cent of the Imperial clay and 4.96 per cent of the Holtville clay — the two fine-textured soil types — in contrast to only 3.21 per cent of the Meloland fine sandy loam, 2.78 per cent of the Holtville silty clay, and 2.73 per cent of the Imperial silty clay. Degree of Alignment of Crops with Soils. — The alignment is not marked in the case of the broader groups of crops, although certain relations are indicated. The proportion of each of the several soil types Cir. 334] Soils and Crops of Imperial Valley 37 (Concluded) Holtville Silty Clay Loam Holtville Very Fine Sandy Loam Meloland Fine Sandy Loam ROSITAS Very Fine Sand Melo- land Fine Sand ROSITAS Fine Sand ROSITAS Sand Dune- sand Super- stition Gravelly Sand Total Acreage of Crop, or of Land Use 56 5 36.0 25.43 0.11 141.5 39.93 100.00 0.19 0.06 20.0 17.0 35.04 05 48.5 41.24 100.00 0.07 0.02 78.0 3 5 0.94 0.08 60.5 16.28 0.19 32 8.61 23 4.0 1.08 19 1.5 0.40 0.03 371.5 21.01 100.00 0.27 0.17 25,203.5 2,963.0 28,149.5 11,285.5 1,281.0 2,464.5 752.5 1,057 5 164.0 171,622.5 14.69 1.73 16.41 6.57 0.75 1.43 44 0.61 0.10 100.00 85.64 64.58 87.63 80.02 62.31 46.75 34.73 19.50 21.88 78.43 4,224.5 1,624.5 3,969.0 2,816.5 774.5 2,807.0 1,414.5 4,368.0 585.5 47,186.5$ 8.95 3.44 8 41 5.95 1.64 5.95 3.00 9.26 1.24 100.00 14.36 35.42 12.37 19.98 37.69 53.25 65.27 80.50 78.12 21.57 29,428.0 4,587.5 32,118.5 14,102.0 2,055.5 5,271.5 2,167.0 5,425.5 749.5 218,809.0 13.47 2 10 14.70 6.44 0.94 2.41 0.99 2.48 34 100.00 100.00 100 00 100.00 100.00 100.00 100.00 100.00 100.00 100.00 30,314.0 4,587.5 32,541.0 14,114.0 2,055.5 5,271.5 2,167.0 5,425.5 749.5 225,329.5 gravelly sand; 18.0 acres of unused land on Superstition fine sand; and 20.5 acres of unused land on Carrizo sand. utilized for crop production suggests that the two finer-textured and the four coarser-textured soil types were found, as might have been ex- pected, to be less well suited for crops in general than are the six exten- sive, intermediate ones. The plantings of "all forage, hay, and grain" (except sorghum), however, are located largely on the medium to fine- textured soils, while the plantings of "all truck crops" tend to be con- centrated on those with medium to coarse textures. Somewhat more distinct localizations, reflected to lesser degree in the distributions of these major groups, are found to occur in the cases of the individual crops. Barley, Wheat, and Oats. — The most striking of these is the concen- tration of "barley, wheat, and oats" on the clay members of the Im- perial and the Holtville series. As stated earlier, barley has long been 38 University of California — Experiment Station one of the more satisfactory crops in the utilization of the fine-textured, less valuable soils. Wheat and oats are more exacting as to soils than is barley; consequently, in contrast to barley, they must compete with other, more remunerative crops. The barley acreage, four times that of wheat and oats combined, is definitely associated with the two fine-tex- tured soils — Imperial clay and Holtville clay. This association is em- phasized further by the fact that only one of the soil types having a tex- ture coarser than that of a silty clay has as much as 2.0 per cent of its area planted to grain. This exception, Meloland fine sandy loam with a percentage of 3.2, is a result of several large plantings of wheat on this type. If a more detailed differentiation between these three grains were made, it is probable that an even more definite alignment would be found between barley and the two fine-textured soil types. Alfalfa. — In contrast to the small grains, alfalfa has a relatively uni- form distribution on almost all the soil types, as is strikingly shown by the distribution map, figure 8. The absence of any definite alignment is due primarily to the part played by this crop in the local agricultural sys- tem. Alfalfa is planted on considerable acreages in connection with the livestock industries. Furthermore, truck farmers will pay higher rents for lands that have been in alfalfa, and many owners grow it on soils better adapted to truck with the definite plan of leasing the lands later to truck farmers. For these reasons, alfalfa is planted on 30 to 50 per cent of the total extent of each of the more important soil types, with the exception of the fine sand members of the Meloland and Rositas series. Bermuda Grass. — Although Bermuda grass is never sown by local farmers it is disseminated throughout the Imperial Valley where it is considered as much a crop as a pest. As it grows best during hot weather, withstands heavy pasturing, and is notably tolerant of alkali, Bermuda grass is favorably regarded by dairymen and others who require sum- mer forage. The more than 10,000 acres of Bermuda pasture mapped in the crop survey represents, in general, unsuccessful attempts which were made at an earlier date to secure satisfactory stands of alfalfa or other crops. Due to soil conditions, cultural practices, or perhaps even to a change in the farm program, Bermuda grass invaded a field and soon replaced the original planting. If summer pasturage was desired, the farmer accepted the situation and provided the invader with water for its continued growth. This fortuitous origin of Bermuda pastures is re- flected by the irregularity in percentages for the several soil types. Cotton and Grain Sorghum. — Neither cotton nor grain sorghum is fully representative of the usual summer distribution and no reliable conclusions may be drawn from the mapped occurrences of these crops. Cm. 334] Soils and Crops of Imperial Valley 39 In the case of cotton, however, the percentages are high for the two fine- textured soils with which this crop is usually associated. The rather high percentages of Imperial silty clay loam and Rositas very fine sand planted to cotton are largely results of two erratic plantings — one of 60 acres on the Imperial soil, and one of 71 acres on the Rositas soil. Lettuce. — Lettuce, one of the two remaining crops having an extent of more than 5,000 acres, has been important commercially only since 1919. Its distribution, however, shows some alignment with the medium to fine-textured soil types, on which the larger yields and firmer heads are produced. This is reflected in the rather high percentages for the silty clay and silty clay loam members of the Imperial and Holtville series. The high value in the case of Meloland fine sand is the result of three somewhat erratic plantings in the Mount Signal district, south- west of New River, recently entered by the truck-farming industry. The dot map showing the distribution of lettuce (fig. 8) when compared with the map showing surface textures (fig. 4) suggests this alignment, although it is not particularly well denned. Cantaloupes. — Cantaloupes, the second most extensively planted truck crop, have been commercially important for many years. This crop and lettuce are in many cases produced on the same fields, one fol- lowing the other, the plantings of the former usually being associated with the medium-to-coarse-textured soil types. These soils, owing to their better drainage, are more favorable for an early harvest than are those of finer texture and so permit of higher returns to the growers. This is reflected in the relatively high percentages in the cases of the silty clay loam members of the Imperial and Holtville series, of the Melo- land fine sandy loam, and of the Rositas very fine sandy loam. The rela- tively extensive plantings of cantaloupes on Rositas sand (like that of lettuce on Meloland fine sand) is the result of a recent expansion of truck farming into the new Mount Signal district. The dot map showing the distribution of this crop (fig. 8) when compared to the map showing textures (fig. 4) indicates a rather definite alignment, especially in the Westmoreland district. Grapes and Grapefruit. — Plantings of grapes and grapefruit are of relatively small extent and the alignment is no more than slightly sug- gestive. There is nothing notable about the distribution of the grape acreage, other than the avoidance of very fine and of very coarse-tex- tured soil types. The relatively high percentages for grapefruit on the silty clay and the silty clay loam of the Imperial series is the result of a very large, recent planting on these two soil types. These orchards have not grown well and are proving the undesirability of planting on these soils. The relatively high acreage in the case of Meloland fine sandy 40 University of California — Experiment Station loam, however, is based upon many small plantings, including numerous older groves, and probably is more nearly indicative of a satisfactory crop-soil combination. Considering the alignments from the standpoint of the individual soil types, other notable aspects of the crop-soil combinations are evident. A striking similarity in utilization exists between the two members of each of the three pairs of finer-textured soils : The clays of the Imperial and Holtville series are planted predominantly to small grains (chiefly barley) and to cotton; the silty clays of the two series are used to ap- proximately the same degree for all of the more extensively planted crops with the possible exception of melons; while the silty clay loams, in contrast to the clays, are used only slightly for small grains and to an important degree for lettuce and melons. The Meloland fine sandy loam is used rather extensively for most of the major crops, and dunesand — a portion of which has been brought under cultivation — is used not at all for small grains or cotton, to only a minor extent for alfalfa, but to a notable degree for melons, tomatoes, grapes, and grapefruit. Although no pronounced alignments of crops and soil types are demonstrated, the 1927 measurements nevertheless suggest a trend in planting toward a more rational use of the soils. IRRIGATION AND SOIL MANAGEMENT Irrigation must be relied upon entirely for the production of any crop in Imperial Valley. The intelligent application of irrigation water is of paramount importance, not only to the production of the crop, but to the maintenance of a productive soil. Underirrigation is sometimes the cause of crop failure. This is especially true of crops grown on the fine- textured types of soil. Overirrigation, on the other hand, is more gen- erally the case and often results in a rising water-table, improper aeration of the soil about the crop roots, and the ultimate accumulation of alkali near the surface of the soil. "Soft," "Medium," and "Hard" Soils.— The farmers of the Valley usually classify soils in this region as "soft," "medium," or "hard." The "soft" soils are the sands, sandy loams, and silt loams; "medium" soils are silty clay loams and clay loams, while the "hard" soils are the clays. This classification, however, is very misleading, as it alludes to the sur- face soils only (fig. 4), and does not take into account the character of the subsoils (fig. 3), which in many cases determine the ultimate suit- ability of a soil for a particular crop. It is essential that one should know the soil conditions required for the crop he has chosen to grow. Soil and crop must be compatible if good results are to be had. Cm. 334] Soils and Crops of Imperial Valley 41 When the proper soil type for the production of a given crop has been determined, then irrigation, drainage, tillage, rotation, etc., are next in order. The successful farmer in this section is familiar with these sub- jects, and realizes the importance that should be attached to a thorough understanding of them. Irrigation, of course, is of the utmost impor- tance, and with it drainage is closely allied. The natural drainage afforded by the New and Alamo river channels, supplemented as they are by deep, open drainage canals, are unquestionably of great value. But they can be efficient only when the intelligent use of irrigation water is the common practice and not the exception. The use by the farmer of a soil tube or soil auger should be a common practice. 21 For only by the use of such an instrument can he familiarize himself with the soil char- acter of his farm land, and the water requirements of the same. Some- what more than half of the soils in this Valley are. underlain within a depth of 6 feet by dense and almost impervious clay. If the surface soil is of a character easily penetrated by irrigation, yet of shallow depth and underlain by an impervious subsoil, as are the members of the Meloland series, drainage often becomes difficult, and rise of ground water results. With this soil, great care must be exercised in irrigation, as both the production of a crop and the maintenance of a productive soil are at stake. However, there is much land in the Imperial Valley on which the surface soil is such that the penetration of water is very slow and difficult to accomplish (fig. 4). These are the so-called "hard soils," the clays of the Imperial and Holtville series, and underirrigation of crops is not uncommon. Where soils of this nature are encountered, and it is possible to do so, a shallow drain ditch should be constructed at the lower end of the field to carry off surplus water. This surface drainage makes it possible to run water for a longer time than would otherwise be feasible, permitting the penetration of moisture to a greater depth, and materially assists in preventing the rise of alkali. It is not, however, that any appreciable amount of alkali is removed from the soil by this surface drainage, but rather that it is carried to a greater depth by the deeper penetration of moisture. Only where underground drainage is present or provided, can the ultimate removal of alkali in any appre- ciable amount, be effected. Moisture Available to Plants. — The farmer should keep well in mind the relation of total moisture to available moisture in the several soil types. Not all the soil moisture is available to plants, and the amount that is available varies with the soil type. For example, the moisture content required by some of the clay soils to prevent wilting of a crop, 2i Cosby, Stanley W. A general purpose soil auger and its use on the farm. Cali- fornia Agr. Exp. Sta. Cir. 306:1-4. 1926. (Out of print.) 42 University of California — Experiment Station is more than twice the amount required by the same crop on some of the silty or sandy soils. Therefore, the number of irrigations and the total amount of water required to produce a given crop depends on the char- acter of the soil on which the crop is grown. Cultivation of Soils. — Creating and maintaining the proper physi- cal condition of the soil cannot be too strongly urged. Irrigation is not a suitable substitute for cultivation, and should not be used as such. With a fine-textured soil in poor physical condition, irrigation by the ordinary method does not penetrate to the desired depth to induce deep-rooted plants. The result of crops grown under this unfavorable condition is low yields and poor quality, or complete crop failure. When practicable to do so, as with row crops grown on the medium to fine-textured surface soils, cultivation after irrigation should be the common practice. The breaking up of the surface of a hard, compact soil aids greatly in aeration. The roughened, cloddy condition of the surface caused by culti- vation is of material assistance in checking the flow of water in the next succeeding irrigation, thereby causing deeper and more effective pene- tration of moisture. Care should be exercised in cultivation to avoid injury to the root system, although in preparing soil of this nature for crops, deep tillage is of material advantage. The use of a soil chisel or subsoiler that will loosen the soil to a depth of 15 inches or more is effective in that it makes possible the penetration of moisture to the de- sired depth previous to planting the crop. Incorporation of Organic Matter. — The common practice among farmers for improving the physical condition of the soil is to turn under large quantities of organic matter. This is best done by planning a syste- matic rotation of crops that will provide for the growing and turning under periodically of leguminous green-manure crops. The incorpora- tion of organic matter in this way adds "body" to coarse soils, while it loosens the finer-textured and denser soils, making them more friable and easier to cultivate. Liberal applications of barnyard manure give similar results, and should be added to the soil at every opportunity. The liberal use of leguminous crops, or manure, adds not only humus to the soil, but also appreciable amounts of nitrogen. The soils of this region are naturally deficient in both of these constituents. Alfalfa is the most logical crop in use in rotation with other crops grown here. Usually truck crops such as cantaloupes, lettuce, etc., can be grown three or more years in succession on land on which a good stand of alfalfa has been previously maintained. But it is not necessary, and in many cases not even desirable, to use alfalfa regularly in the crop rotation. It is often more profitable to use annual legumes, or manure, supplemented when necessary with commercial inorganic fertilizers, Cm. 334] Soils and Crops of Imperial Valley 43 3 > I 04 * M O En » w 5! el 2 O 5 3 S a) •2r o. -da -3 a crt 3 « »0 N M N O il O —I —I -< § s "d a> <» a> a s -c s ^ 06 0D m ?5 3 3 3 M o T3 .s-s 00 (0 — " OQ ■Cd B13 3 3^3 2 3 2 2 O O 3 o a a o a ■^ "d "O a § g § & M h h +> -a .a -a g (h Pi «* •** o o o w 'O 'O ~0 co t) Oi t) j; "C 'C 'C *i t3 "O *& a •8 -8 -8 3 3 3 cp Xi o o a a o o CO CO 0Q 3 3 O a CO 1-1 T-l ~H ■*! 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T i T J T 5 T t ) t; i T 3 ft o .tJ .B O e ) C 3 C ) c > c 3 O 03 o *03 0303OOOOOOOO0, "S 5 O c 5 C > C > c ■> c 3 O O fa h^OOOOOOOOfi pt O C : c 3 C C 5 C 3 O ^ N^ v ~ y ft ! ^9 ? ; as « : >h > a f. i O u ! -S 3 CD > o i 1 P i j ( I C P 1 a P j f c i 7 1 3 J 1 1 c V 3 3 3 2 i i 7 3 I 03 CD 43 >> O 02 c q: t 6 5 5 2 43 w CD > CD 78 University of California — Experiment Station earlier in the season, it being- more sensitive, to heat. Very good yields of fair-quality grain are produced from the varieties now in common use. Wheat produced in this region is usually disposed of as feed grain. During recent years, older varieties have been gradually eliminated until at this time a large percentage of the wheat acreage is devoted to the White Federation variety. It is well adapted and dependable. In table 18 will be found the yield data of five varieties of wheat planted at the experiment station on November 27, 1929, and harvested April 28, 1930. These data are from five replicated plantings of each variety. TRUCK CROPS Imperial Valley and adjacent areas hold a unique position in the pro- duction of many important truck crops. Climatic conditions here are almost ideal for the production of winter vegetables. The large number of sunshiny days, the mild temperature, and the abundance of water for irrigation make it possible to produce many crops during the winter months that cannot be planted in less favored regions until spring. These conditions give a very distinct advantage in the ready sale and higher prices for early vegetables. A large number of crops can be grown in the open fields during the coolest weather without protection. This group of plants includes beets, carrots, cabbage, cauliflower, chives, chicory, collards, dandelion, endive, garlic, horseradish, kale, kohlrabi, leek, lettuce, mustard, onions, parsley, parsnips, peas, radishes, salsify, spinach, turnips, and others. Such crops as cantaloupes, cucumbers, squash, and tomatoes must have some protection if grown during the winter months. For this purpose, glazed transparent paper caps or covers are used. These are often referred to as "hot caps." In addition to this, some of the early plantings are protected by wigwams of arrow- weeds and newspapers built about the plants, leaving the south side open. Later in the season, when danger of frost and wind damage has passed, these covers are removed. With practically all of the commercial truck crops grown in this region, earliness is the keynote to success. In the first place, suitable soil must be selected. The well-drained sandy soils, such as the Rositas fine sandy loam, produce the earliest crops. The medium-textured soils give satisfactory yields of high quality, while the fine-textured soils such as Imperial clay, are the least suitable. The use of alfalfa in rotation with truck crops has been a common practice for many years. The application of liberal quantities of stable manure, and the growing and plowing under of covercrops are proved methods of increasing yield and hastening maturity. When covercrops Cm. 334] Soils and Crops of Imperial Valley 79 are used, they should be plowed under in time to be completely decom- posed before the truck crop is planted. From 30 to 60 days will be required for this, according to the crop used, and the moisture condition of the soil. Thorough preparation of the seed bed, and careful, frequent cultivation are strongly urged. Irrigation of practically all truck crops is by the furrow method. The shallow-rooted annual crops in this group require lighter but more frequent irrigation than the perennial or permanent crops. Insects injurious to truck crops are numerous, and must be constantly guarded against. A planting calendar for truck crops (table 20) appears at the end of this section. Artichokes (Cynara scolymus). — The globe artichoke is a hardy perennial and produces very well. It has been grown commercially on a small scale and the product sold locally. Large plantings are not recom- mended, as the crop is better adapted to the coastal region where the industry is well established. Artichokes should be propagated by rooted cuttings made from productive plants. The plants may be set from December to February, and should be spaced from 4 to 6 feet apart in both directions. From 1,200 to 2,722 plants per acre will be required, depending on space given. The crop is harvested April to June. Asparagus (Asparagus officinalis). — This crop has proved to be one of the most reliable truck crops grown in this region. It is well adapted, and failures with this crop have been traceable to improper soil selection, or to the cultural methods used. The plant is perennial in duration, and, as with any other permanent crop, the utmost care should be exercised in selecting suitable soil. Coarse to medium-textured soils are highly desirable, as early production is essential. In addition to choosing good soil, large quantities of barnyard manure should be applied to supply the necessary humus and nitrogen, which are essential in increasing yields, improving quality, and inducing earliness. Ten tons or more of good barnyard manure supplemented by 500 pounds of ammonium sulfate per acre may be used. The soil preparation previous to planting should be thoroughly done, and Bermuda grass and other noxious plants completely eliminated. The establishment of Bermuda grass in aspara- gus fields must be carefully and constantly guarded against. Frequent thorough cultivations are necessary, and considerable hand work with hoe and shovel will be required. Asparagus is not ready to harvest until the second year after seeding, or the first year after setting the seedling plants in their permanent place in the field. Some growers prefer to purchase the one-year-old seedlings from the nurseryman and transplant them directly into the 80 University of California — Experiment Station permanent field. Others plant seed and grow, their own plants. If seed is used, the planting should be done from January to mid-spring in double rows, 3% feet apart, with the plants spaced about 6 inches apart in the row. The use of low beds is advisable. When one year old, the seedlings are transplanted into the field in trenches 8 to 10 inches deep, in rows 6 to 7 feet apart, and 16 to 18 inches between plants. One year after this permanent planting, the first crop will be ready to harvest for market. Cutting begins the first of February and usually lasts from 6 to 8 weeks. The length of the season depends largely on the arrival on the market of asparagus in large quantities from other sections. After the spring harvest has been discontinued, the asparagus is irri- gated and allowed to grow to maturity. Large, well-developed tops being essential, irrigations should be given as the plants and soil require, to gain this end. The mature tops are cut and burned in December, and the plants irrigated soon thereafter to start the new growth. When fall harvesting is practiced, the tops are cut or disked in late September. The plants are then irrigated immediately. Beans (Phaseolus spp.). — (For commercial dry beans, see "Field Crops.") Green beans are not extensively grown in this region. They are very sensitive to cold, and even in this mild climate, must be grown as either a spring or fall crop. Good seed-bed preparation is essential, and a fertile, well-drained, loamy soil is the most desirable. Frequent light cultivation should be given until the plants begin to bloom. Care should be taken to avoid any damage to the roots, and to cultivate only when the plants are dry. Beets (Beta vulgaris). — Beets of all varieties are well adapted, but must be fall planted and grown as a winter crop, because they are very sensitive to heat. Table beets are not important as a commercial crop. Brussels Sprouts (Brassica oleracea var. gemmifera). — This crop does fairly well in home gardens. It matures more slowly than cabbage. Cabbage (Brassica oleracea var. capitata) . — Cabbage has been grown successfully as a winter crop in this region. In commercial plantings, seed is planted directly in the field in September or October, and the seedlings are later thinned to 18 inches apart in double rows 3% feet apart. Harvesting is done in January to April. Good clay loam soil should be used, frequent light irrigations given, and thorough, deep cultivation practiced. Cabbage worms and aphid must be carefully guarded against as they often do serious damage. Other members of the cabbage family that are well adapted here as winter crops are cauliflower, Brussels sprouts, broccoli, kohlrabi, kale, mustard, and collards. The culture for all of these is very much the same Cm. 334] Soils and Crops of Imperial Valley 81 as for cabbage, except that the spacings vary with the different crops. Of this list, the cauliflower and Brussels sprouts are most important. The cauliflower is not quite so hardy as cabbage and requires more careful handling. Carrots (Daucus carota var. sativa) . — Carrots planted in the fall make a very dependable crop for this section, and one that has grown into considerable importance in recent years (fig. 9) . A good loamy soil, »£* Fig. 9. — Harvesting a field of carrots in Imperial Valley. preferably sandy loam, should be used. Plantings made in September are ready to harvest in January, and later plantings are harvested in the spring. Carrots are grown in double rows on ridges. They should be irri- gated and cultivated frequently. Cauliflower (Brassica oleracea var. botrytis). — This crop is not quite so hardy as cabbage and requires more careful handling. Its cul- ture is the same as that described for cabbage. Chard.— (See "Swiss Chard.") Chicory (Cichorium intybus) . — Chicory has been grown successfully on a small scale as a salad plant. Planting may be done in the fall, using a light, rich, and deeply worked soil. Plant in double rows as for lettuce, but space the plants 6 inches apart in the row. Chicory is often confused with endive. They belong to the same genus and family of plants, but are different species. Chives (Allium schoenoprasum) . — Chives may be grown in the home garden, the culture being the same as for green onions. Collards (Brassica oleracea var. acephala) . — This crop is of little importance. Its culture is the same as for cabbage, but it requires a longer growing season. 82 University of California — Experiment Station Cucumbers (Cucumis sativus). — Cucumbers have been grown com- mercially for a number of years, and are well adapted. They should not be planted in the open until after the danger of frost, but may be planted under covers in January. Their general culture is very much the same as that of cantaloupes, except that cucumbers require more frequent irrigation. Fall crops are successfully grown from plantings made August 10 to 30. Cucumbers grown here are marketed for slicing purposes. In growing a crop of cucumbers, the attacks of aphids, nema- todes, mildew, and beetles must be guarded against. Dandelion (Taraxacum spp.). — This crop is well adapted and has been grown successfully as a salad or greens crop. Sandy loam soil should be used. Its culture is the same as that recommended for lettuce. Eggplant (Solanum melongena) . — Eggplant is well adapted here. It is resistant to heat, but very sensitive to frost. The seed may be planted under protective covers in January in rows 3 feet apart, and 3 feet between plants; or they may be planted in the open after all danger of frost has passed. Eggplants require an abundance of water and fre- quent cultivation. Endive (Cichorium endivia) . — Endive is another highly prized salad plant that is well adapted as a winter crop in this region. Its culture is the same as for lettuce. Endive is often mistaken for chicory. Garlic (Allium sativum). — This crop has, at times, been grown com- mercially, and is well adapted here. It is a perennial plant of the onion family, and may be grown from sets (cloves). Its culture is about the same as for onions. When the plants are mature, the leaves turn yellow, at which time they should be pulled and the bulbs dried in the shade. Horse Beans. — (See under "Field Crops.") Kale (Brassica oleracea var. acephala). — This is one of the common greens crops, and has been grown with success during the cooler months of the year. Its culture is the same as described for cabbage. Kohlrabi (Brassica oleracea var. caulorapa). — This crop is well adapted. It is a member of the cabbage family, but its culture should be the same as described for turnips. Lettuce (Lactuca sativa). — Lettuce is one of the major crops of this region (fig. 10). It is well adapted to winter culture and succeeds on a variety of soils. Clay loam soils produce earlier crops than do either the heavier or lighter types, but high yields of excellent quality are pro- duced by the clay soils. Silty clay soil is the choice of many lettuce grow- ers. Whatever the soil type selected may be, the seed bed should be very thoroughly prepared. If lettuce is not grown in rotation with alfalfa, then covercrops or barnyard manure must be relied upon to supply the needed humus. Sesbania has been used rather extensively for this pur- Cm. 334] Soils and Crops of Imperial Valley 83 Fig. 10. — Upper: Smoothing ridges and planting three double rows of lettuce at one operation. Middle: Harvesting lettuce. Lower: Packing lettuce for shipment. 84 University of California — Experiment Station pose on the clay soils, and has proved to be very satisfactory. Barnyard manure has also given excellent results from both experimental and commercial plantings. After the soil has been thoroughly worked to a considerable depth, and has been well leveled to insure perfect irrigation, it is furrowed into rows 42 inches apart, The seed is drilled in double rows about 12 inches apart on each of these ridges, and later thinned to plants 12 inches apart in the row. Thinning should be done when the plants have two to four leaves. Proper irrigation is vitally important. A considerable amount of moisture should be present at all times, but under no circumstances should the plants be flooded. Small streams of water run in furrows for a long time will have the desired results. If the temperature is favorable, planting may be done as early as September 20. However, most of it is done from October to December. 24 A considerable amount of lettuce in this section is |ertilized with superphosphate. When this is used, it is spread on the level ground at the rate of 250 pounds per acre, and the seed beds raised directly over the fertilized strips. Melons (Cucumis melo). — The cantaloupe is the most important variety of melon grown in this region and is one of the major crops of Imperial Valley. Cantaloupes, together with the Honeyball and Honey- dew melons, sometimes utilize more than 36,000 acres of land in a single season, with about 75 per cent of this acreage devoted to cantaloupes. The culture of these varieties, as well as that of the Persian and Casaba melons, is practically the same. There is, of course, difference in the spacing and date of planting. Good loamy soil, well supplied with organic matter, and a thoroughly prepared seed bed are essential to the profitable production of melons. Old alfalfa land is especially suitable, but organic matter can be sup.- plied by growing and plowing under covercrops, or by applying barn- yard manure to the land. All cantaloupes and related varieties of melons are grown on raised beds and irrigated by the furrow method. The rows should run east to west, and the seed should be planted on the south slope of the raised beds. The plants are trained to the north, over the top of the beds, and thus contact of irrigation water with the fruit is avoided. All melons planted previous to February 15 are protected by covers (fig. 11). About 60 per cent of the total acreage is planted under covers and a small percentage, for the very early market, is both covered and 24 For more complete information see : Jones, H. A., and A. A. Tavernetti. The head-lettuce industry of California. California Agr. Ext. Cir. 60:1-48. 1932. Cm. 334] Soils and Crops of Imperial Valley 85 Fig. 11. — Upper: Early cantaloupes planted under "hot cap" covers. Middle: Cantaloupes for the very early market grown under "brush" protectors made of arrow-weeds and newspapers. Lower : Harvesting a crop of cantaloupes. 86 University of California — Experiment Station brushed. The brushed acreage — planted under brush and paper wig- wams — does not exceed 2,000 acres per year. About 50 per cent of the Honeydews and 33 per cent of the Honeyballs are planted under paper covers, and some are brushed. Persian and Casaba melons are planted in the open after danger of frost. The chief enemies of the melon family in this section are aphid, mildew, cucumber beetles, and nematodes. Mustard (Brassica juncea var. crispifolia) . — Mustard is well adapted and makes an excellent greens crop. It should be planted in the fall and harvested during the winter and early spring. Mustard is also used as a soil-improvement crop (table 6). Okra (Hibiscus esculentus). — Okra is perfectly at home in this re- gion. It may be planted in the open as soon as danger of frost is past, and will succeed when planted as late as July. The seed should be planted in rows 3 feet apart, and the plants should be thinned to 12 inches apart in the row. Clean cultivation and moderate irrigation should be given. Okra is valuable for its edible pods which are used in soups and stews, and in many other ways. The young pods should be picked about every second day during the fruiting season, as they grow very rapidly and soon become tough and valueless. Onions (Allium cepa). — Onions have been successfully grown in this general region for a number of years. This crop is best adapted to the sandy loam and silt loam soils, and most thorough preparation of the land is essential. Plowing, disking, harrowing, and floating are usually necessary to put the soil in proper tilth. Flat-topped ridges are pre- pared, as for lettuce, except that the rows should be closer together. The furrows should be 3 feet apart, and the onion seed drilled in double rows 1 foot apart on the top of the ridges. Frequent irrigations are necessary during the growing period, but water should be gradually withheld as the plants approach maturity. Cultivation, including hand-hoeing and weeding, is a very necessary part of onion culture. Planting may be done from September to November, and harvesting from March to May. Many growers plant seed in September and transplant in December. Parsley (Petroselinum hortense). — Parsley is of relatively little commercial value, but does well as a winter crop. Its culture is the same as that of lettuce. Parsnips (Pastinaca sativa). — Parsnips do well in this section. They require a rich soil and cultural methods as described for carrots. Peas (Pisum sativum). — Peas are of considerable importance as a winter crop. They are adapted to a variety of soil types. Like many other row crops, peas are planted in single or double rows on raised beds, and irrigated in furrows. Most spring plantings are made in single rows. The soil should be well prepared and in prime condition at the time of seed- Cm. 334] Soils and Crops of Imperial Valley 87 ing, for excessive moisture will cause pea seeds to rot. The seed should be planted in the moist soil and not irrigated until the plants are well up. After the plants are up, they should be irrigated frequently enough to keep the soil moist, and the plants in a thrifty condition. They should be well cultivated between irrigations until the vines begin to run. If frost occurs when the plants are in blossom, or while the pods are young, considerable damage is done. Grasshoppers sometimes seriously damage young pea plants, and aphids are always a menace to the crop. Peppers (Capsicum sppj. — Peppers have produced profitable crops when grown in favorable localities in this region. A coarse-textured alkali-free soil should be used. Peppers may be planted in December or January, and transplanted in the field after danger of frost is past; or the seed may be planted in the field if protective covers are used. The permanent planting should be in rows 3 feet apart, with 2 feet between plants in the row. Peppers require an abundance of water; and clean cultivation should be practiced. If a hotbed is used, the seed should be planted from September 15 to October 15, and the transplanting done from February 15 to 20. Potatoes (Solarium tuberosum). — This crop cannot be said to be adapted, as it is sensitive to both the cold of winter, and the heat of sum- mer. It must, therefore, be grown during a relatively short season in the spring. If a coarse-textured, fertile soil is used, and weather condi- tions are favorable, profitable crops are usually grown. Early maturity is essential. In the cultivation of potatoes, the soil should be kept uni- formly moist by frequent light irrigations, but saturation should be avoided. Water should be gradually withheld as the crop matures. The western potato stalk-borer is probably the greatest menace to this crop. Pumpkins (Curcurbita pepo). — The pumpkin is well adapted here, but is a crop of minor importance. All varieties do well. Best results are obtained when the seed is planted in the summer about July 1, so that the fruits will mature in the fall just before frost. Radishes (Baphanus sativus). — All varieties of radishes are well adapted and do best on the lighter-textured soils. They may be planted at intervals from September 1 to April 1. Seed should be planted in a deep well-prepared soil and irrigated frequently. Quick growth is es- sential to the production of crisp tender roots. Roselle (Hibiscus sabdariffa). — Roselle, the buds and young leaves of which are used in making jelly, grows well in this region. It is not particular as to soil type and is easily grown. Roselle requires a long growing season, and should be planted as soon as danger of frost is past. Salsify (Tragopogon porrifolius). — Salsify may be grown by the 88 University of California — Experiment Station same methods as those recommended for parsnips and carrots. The soil should be loose and deep and should be kept moist at all times. Spinach (Spinacia oleracea). — Spinach is very well adapted and may be grown during the cooler months from fall to spring. The soil should be well worked and contain an abundance of organic matter. Liberal irrigation is essential. It should be planted in double rows, as for lettuce. Sweet Corn (Zea mays var. rugosa). — Sweet corn is grown commer- cially to a limited extent. Spring plantings often fail if hot weather is encountered during the pollinating period. Fall plantings are usually more successful. Sweet corn should be planted in rows 3 feet apart and 18 inches between plants. Fertile soil should be used, and the crop should be irrigated and cultivated frequently. The attack of the corn earworm is sometimes serious. Sweet Potatoes (Ipomoea batatas). — Sweet potatoes have been grown successfully in this region for a number of years. The crop is well adapted, but requires very careful handling. Coarse-textured soil must be used, and intelligent care exercised in the application of water. If the growth is forced, the result will be coarse, poor-quality potatoes; but if properly handled the quality is usually good. Seed potatoes should be planted in hotbed in February and transplanted into field in March. Swiss Chard (Beta vulgaris var. cicla). — This vegetable, which is a member of the beet family, is valuable for its crisp succulent tops. It produces well on a variety of soils. By picking the older, outside leaves and allowing new growth to develop from the center, the plants will pro- duce over a long period of time. Tomatoes (Ly coper sicon esculentum). — Tomatoes for early produc- tion must be planted under protective covers in the field. For early and heavy production, a light-textured soil rich in organic matter should be used. Tomatoes are often planted under covers and brushed, as described for cantaloupes. Turnips (Brassica rapa). — Turnips can be very easily grown during the winter and early spring. They do best when planted in raised beds in a rich loamy soil and irrigated by furrows. Frequent irrigations are necessary to force a rapid growth, and produce a crisp, tender product. Watermelons (Citrullus vulgaris). — Watermelons are well adapted, and Imperial Valley is noted for its early production of this crop. The culture is the same as that described for cantaloupes and other melons. Well-prepared, coarse-textured soil must be used. Planting may be done under covers in December, or in the open field after the danger of frost is past. Because of the prevalence of the watermelon- wilt disease, it is not safe to plant the common wilt-susceptible varieties on the same land more often than once in 12 or 15 years. Cir. 334] Soils and Crops of Imperial Valley 89 2 09 •r a > < CD c c go 1 X 2,500-5,000 pounds 3,000-6,000 pounds 3,000-6,000 pounds CO 3 TO CU oS t-. u TO E B TO 4- 1 O GN TO 4> c IN TO 3 c CO TO bC _3 O O CM a > c3 O Q 1 " o.^Oooo|«».«..Soooc : loo p,oo c^ ^H ,_l •' H i-I _m34>d0}S~H_H_,i-H S' _l h>'03_,'-H t *i3 ^^H^H'-I_it. a'SOoaoo^.ft^o.^a-^ggoj c3 c oa jC a) ^3 a oo3o3 a g'4>o3Z m2 . d fl £ 0Q«g- TO TO f7-( TO TO TO 0! i> to to to to i>+j-u^S 4> o> 4> 4> j3 m cu m m to to to to ,3 to m O 5 .2 .3 .3 .5 O 45 ^ oo .5 .5 .5 .3d 3 d .5 oo .S 4 «? SS 5 ,g 3 a a «£ «, «> <» » .5 - ^ , CD CD tC tO ^H _L L. JL -fJ CO ,-h ^H ,—t *— 1 CNI A iiiiO co co cm ■ oo •*• ~m o » »n « i i i i «N 2 * m M M ^2^ <^ d> -p "a 4) 0) 41 4 «*i «t-i 4) **- CO CO CO CC I t c. : 1 1-3 i • d : : : O ; +s +3 hJ 4) -t- 4) 4) OJ 4) 4 4) 4j 4> "+- CO CO CO CO CO .3 %> 3 a) ^ a TO TO d b -2-S OOO c^O r- i>- co co ^ ^ ^ t^ OO o *> a 3! 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C 0) O 1 CO CO CO CO CO 43 0> OffltH > (M CO CO CO CO -1- -Tj ■I •- 3 o o E s o o o o o CO CO CO CO CO eo co co -g o I o sa ° fc fc S a a a a ^ S ^ tg ^ Cg ^ tS o -+J o o o o O -^ -WOO © O 0> OOfeco a a a a +? v v oi oi x W CO 02 cc O o o o = o »o g £ sf ^ a ^ „ e © s 5 <: o - 1 o o _o o _o w g 5 ^ >,- ^^ >, >> a 11 a -o a 0) ,01 01 CO fi «2 O^ ^ ^ _ 43 -^ a ' rv, 8 & a, o .g »h c3 (3 S rt O fl 5? O Q ^ 5? c3 c3 c3 c^ c3 9 G I mper I mper Imper Imper 3 ■£ • - O > £ a 13 !> oi ^ o3 73 -w oo 3 3 b o o ,_ .b o 5 ooooo 3o300 OOOOO hhOO OOOOO -OT3 o O O O ° P o O O- a c3 W O 03 O « O to O 3 w Cm. 334] Soils and Crops of Imperial Valley 91 «*h «*» O 73 .a. IS o> a as c8 o o0^^^oO, M oO, M o 5^o3 5>^>2>ooo Baj^r^ooaSOaSOftSO a & O a 030030030333 ^ fe g u O O < < < < < s a S o> o* 2 2 2 S S 2 2 2 o> o> o> .« >M .rH •!-< • ■"« pj, j^ ^ ^ ^ ' H "" ' H » 00 00 00 ^ >* T|l ^ irtlftlO C3 »( 00 5 a IS c a a a 2 p c T a fl M 4 HE c -c -- a X ', c t a c er > ) -<- a a a a +. a G < or - C o .a ^ O CQ t* o o o o o o o o bm m-# m-* »C050i 00 00 00 rt ,-< r-l . OOOi— ir-ii— i o «o to O J § ^ a 00 0> pq SHOo2i H 5i rt 5 s ^ 5 <§" rt . ° js ^ » S o2^"2 W •« .WW rt j2 H JJ rt ij 3 .£2 3 .O '""' .J .V" .J '""' _,J hhh ■'"!'"! - *> > - ^ f> - ■*> f> - +3 > .+; >^ m2 ti^ ti^^^ . . .M.^.u.rtoO'rtoO'TjoO ^j«Ot3oO .3 .3 ■ 3 tl r. tl O O ►? OQ 0Q QQ CO CO CO CO b 4 ^ Sgg Variety recommended IE O | '5 x: a C C 15 XI £ _3 "E H .2 PC a C u a T 1 > 1 p 01 M S3 o t3 o aS 3 fl 3 c a) a u o o pq >> IS 03 a -a 73 a 73 o o 73 a T o C C C 1 o O 1 o 73 o o o 73 O o T o o O s- '5 O o a 73 O o a 73 o O a 2 O a P- 2 3 P 8 a PL 0) 0J 00 oa 1 a 3 3 02 .2 || a o. 0) ^ Pi o X. 00 (- 0> a a Ph oo o> C % "o ac P C a 3 Ph ■8 92 University of California — Experiment Station < a% cS o Q 1 " Mh .gag 'a o' a" X 3^ pq >>>>>>>> 6 ^S^P^O O O O O O _£ o o o £ o ^ 6 ^ o o d V 83 03 03 8 o § o o o 00000 03 o oh o^ oh^goo o o o o o Q £ £ £ fc 000 dj

03 0> Q; Q) O 03 **"* O 1 03 03 03 03 CO CO CO tO M M tO o o o o >o o o o «J CO CO CO 10 fl o O CO O CO ® CO ft ft ft ft a) 03 CO CO (H U ." O > ft ft a £ o ^* o* 3 -d CO CO CO ^ 03 £ ^ -S > 2 o <=> o CO £ CO £ o o o o 3 g'S'.g 000. h "» ,0 *d _ -a t3 _ -U HH cri >1W in P*> ^J +J • ^> +3 h_> O ft a fe ft ft ft ^ oi

+3 o 03 ^ co ^ S h •"5 -0 ""J l-S §-o§:& M M N> -£ « kH <<«< co co ^ ^ O co ££ (3 „ 03 C3 d hi I §-« S -2 fl -a a M m H £ » Q 03 o> o S ° CO CO CO > > > •■ 1? £ £ i* S 55 c 01 « ir CO CO Q - * O £ M rh J fe di K W O OOOOOQO O ■d t) t) ""d OOOO ■d 'd T3 o 000 9 r°, O ■O OO: ^0 Ph co co co H Cm. 334] Soils and Crops of Imperial Valley 93 FRUIT AND NUT CROPS In the early development of the Imperial Valley, many varieties of both deciduous and citrus fruits were planted. Plantings at the experiment station in 1912 included apples, almonds, apricots, crab-apples, dates, figs, grapes, jujubes, lemons, loquats, olives, oranges, peaches, pears, per- simmons, plums, pomegranates, pomelos (grapefruit), and quinces. In later years many other fruits were planted, but it soon became evident that this region would not develop to any degree of importance in the production of deciduous fruits. Annual crop reports show a gradual de- crease in deciduous fruits, and a more rapid increase in citrus fruit acreage in recent years. Commercial production of deciduous fruits at this time is of very minor importance, but the citrus industry has be- come well established. Many of the deciduous fruits that have failed commercially can be grown for home use to advantage. Before planting any crop of a permanent nature, much care should be exercised in the selection of suitable soil. Most tree fruit crops require a deep, loamy, well-drained soil, reasonably free from alkali. The soil should be free from alkali to a considerable depth, and even with the best soils it is usually wise to flood and leach before planting. Land that has maintained a good stand of alfalfa for a number of years is the most desirable. If alfalfa land is not available, a high-pro- ducing summer covercrop should be grown and plowed under in the fall previous to spring planting. The land should be worked deeply and thoroughly. After plowing, the land should be disked and harrowed. Then it should be given the proper grade for perfect irrigation. The im- portance of properly leveling land before any permanent crop is planted cannot be overemphasized. In the final stages, the use of a good heavy float will be found most useful in filling in slight depressions, and giving a finished appearance to the more or less rough job as left by the buck- scraper. A planting calendar for fruit and nut crops (table 21) appears at the end of this section. Almonds ( Amy g dolus communis) . — Almonds have never been grown to any great extent here. Some plantings have failed almost completely. Other small plantings grown under the most favorable conditions have produced fairly well. Commercial plantings of this crop cannot be recommended. All plantings should contain varieties so arranged as to insure cross-pollination (see planting calendar, table 21). 94 University of California — Experiment Station Apples (Malus sylvestris). — Apples are so out of place in this region that they cannot be recommended even for the home garden. Apricots (Prunus armeniaca). — Apricots are probably as well adapted as any of the deciduous fruits. Earliness, however, is the only distinct advantage this crop has here. Usually, lower yields and inferior quality may be expected as compared with that produced in the best de- ciduous ^fruit-growing sections. Apricots should always be included in plantings for home use. A few small commercial plantings have been maintained for years and have been profitable, but many others have been abandoned. Apricots, as well as many other deciduous fruit trees, have been relatively short lived in this section. Avocados (Persea spp.). — Avocado production has been attempted experimentally in this region many times, but has met with failure in every instance. This crop cannot be recommended even for home gar- dens in this section. Bananas (Musa sapient um). — Banana culture is not at all suited to the climatic conditions prevailing in this region. Blackberries (Rubus spp.). — Blackberries have succeeded in a few small plantings, but show little promise of becoming important com- mercially. Cherries (Prunus spp.). — Cherries have been a complete failure in this region, and plantings should not be made except for experimental purposes. Dates (Phoenix dactylifera). — Dates are ideally adapted to this gen- eral region. The relatively high temperature and low humidity, together with fertile soil and an abundance of water, make up the natural en- vironment essential to successful date culture. Potentially, this is the greatest date-growing region in America, and the industry will no doubt develop more rapidly as offshoots (plants) of the better standard varie- ties become available for increased plantings. Many thousands of seed- ling dates have been planted in this section from which a few good varieties have been developed and propagated; but commercial plant- ings developed from seed or seedling plants are of minor importance. Except for experimental purposes, the planting of date seeds should be avoided. Only offshoots from palms of known variety and production performance should be used in commercial plantings. The varieties grown should be restricted to the smallest possible number that will meet with the soil and climatic conditions, and the demands of the trade. The standardization of fruit processing and packing is essential to the establishment of a permanent market for California dates. It then is obvious that if this is to be accomplished, the number of varieties must be limited. The importance of these recommendations probably will not Cm. 334] Soils and Crops of Imperial Valley 95 be recognized at this time, while the industry is yet in its infancy, and a ready market is easily found for the relatively small amount of fruit now produced. But eventually, as the industry develops, varieties will be eliminated until only a few of the more desirable ones remain under cultivation. Not all varieties are adaptable to the same conditions. For example, the Deglet Noor requires higher temperature and lower humidity than Fig. 12. — A young Imperial Valley date garden. The fruit bunches are covered to protect them from damage by bees and flies. most other standard varieties, and its culture should not be attempted except under the most favorable conditions. This variety is now well established in the Coachella Valley, and will no doubt succeed in certain sections of Imperial Valley. Other varieties recommended for this gen- eral region include Saidy, Zahidi, Khadrawy, Maktum, Halawy, and Thoori. In planting dates, one should recognize the exceptionally long pro- ductive life of the plant, and its potential value. Good soil should be used if the planting is to be a commercial success. Coarse-textured soils of the sandy and sandy loam types have been found best suited to date culture. The date palm will survive when planted on heavy soil containing a high percentage of alkali. It is also drought resistant to a remarkable degree. However, no commercial plantings of value have been developed under such unfavorable conditions. Good soil, reasonably free from alkali, and an abundance of water are vital to profitable date production (fig. 12). 96 University of California — Experiment Station In the early plantings in this region much trouble was caused by the Marlatt and the Parlatoria scales, but in recent years these have been almost completely exterminated. However, growers should be constantly on the lookout for these and other insects and diseases, and if found they should be reported immediately to the County Agricultural Commis- sioner. Dewberries (Rubus spp.). — This crop has in a number of cases pro- duced fairly well and the quality has been good. The crop has not been of commercial importance. Figs (Ficus carica) . — Figs are reasonably well adapted and many va- rieties have been grown successfully. Figs do not drop readily, hence conditions are here unfavorable for drying them and the crop should be marketed as fresh fruit. This is the limiting factor in profitable produc- tion, as the market for fresh figs could be easily oversupplied. The Smyrna variety, which is no doubt the best for drying, will not develop a crop unless it is artificially pollinated (caprified) by the use of the blastophaga (fig wasp) . Fig trees usually bear some fruit when one year old, and if well cared for produce heavily at four years old. Three crops a year may be ex- pected, the second of which is considered the main one. Plenty of water, and a reasonable amount of cultivation, should be given. Gooseberries (Ribes spp.). — These berries are definitely unsuited to this region, and their culture should not be attempted. Grapefruit (Citrus grandis). — Grapefruit or pomelo is the most im- portant fruit crop grown in Imperial Valley. It finds a congenial home in this region and produces fruit of exceptionally high quality in abun- dance. In grapefruit culture, the first important step is the selection of the proper soil type. The fact that this crop does fairly well on a rather wide range of soil types has led to some misapprehension. 25 The ideal soil is a sandy loam, reasonably free from alkali, having good underground drainage, and containing a good supply of plant foods. The soils in Im- perial Valley of major importance to which the crop is best adapted are found in the light-textured members of the Holtville series and the well- drained soils of the Meloland and Kositas series. Soils of the heavy clay types, and all soils containing any considerable amount of alkali should be avoided. The method of soil preparation described under "Fruit and Nut Crops" applies most emphatically to grapefruit culture. This crop, as well as all other fruit crops grown in this section, should have adequate 25 Ellis, Baymond. Suggestions on grapefruit culture in Imperial Valley. Cali- fornia Agr. Ext. Cir. 7:1-18. 1926. Cm. 334] Soils and Crops of Imperial Valley 97 protection from wind damage. The importance of this is very apparent, as a large percentage of the cull and second-grade fruit is so classified on account of wind injury. The athel (Tamarix articulata) and the euca- lyptus are the most used trees for windbreak purposes (see "Wind- breaks"). Protection against sunburn and cold are essential. Extra precaution and care are required until the trees are three or more years old. In some instances, serious damage has been caused by the fire ant (Solenopsis geminata), and growers should be constantly on the watch for this pest, especially in young trees. Flood irrigation tends to protect trees against damage by ants, and the accumulation of salts. All citrus fruits should be consistently fertilized with 5 to 10 tons of dairy manure per acre annually, which should be applied in late summer or early fall. The quality of all citrus fruits, as well as the productivity and length of life of the orchard are determined in large measure by the knowledge and care exercised in selecting well-grown nursery trees propagated from well-selected buds worked on suitable rootstocks. Grapes (Vitis spp.). — Grapes are grown successfully in this section. The industry, however, is confined to the production of early table grapes. Earliness being essential to profitable production, the use of the proper soil type is of paramount importance. Only sandy or sandy loam soil should be used. This fact cannot be overemphasized, as more fail- ures with this crop have resulted from plantings made on fine-textured soils than from all other causes combined. The soil, in addition to being of the proper texture and containing much humus, should be free from alkali and well drained. If the ground water is at a level nearer than 6 feet from the surface, the land should be avoided for grapes. Anyone expecting to engage in the production of table grapes should first familiarize himself with every phase of the culture. Every stage of the cultural process requires intelligent handling. The selection and preparation of the soil, the selection of the variety of grape, the plant- ing and spacing of vines, the staking or trellising of vines, the training and pruning operations, fruit thinning, irrigation, cultivation, and har- vesting all require knowledge and skill. About 100 varieties of grapes have been grown experimentally at the substation, and a like number have been tried in other parts of the Im- perial and Coachella valleys. Of this number, relatively few have shown much promise. The Thompson Seedless (Sultanina) is the favorite, and is most extensively grown at this time. The Malaga, which was once the most popular variety, now holds second place and is on the decline. 98 University of California — Experiment Station Cuttings made from well-seasoned canes of the previous year's growth should be planted in the nursery in February where they should remain for one year. The permanent planting should be made only from well- rooted thrifty vines. The grape leafhopper sometimes causes damage to vines and fruit. Control measures should be used. Thrips are usually present in large numbers, but cause little or no damage. Powdery mildew sometimes ap- pears and causes considerable damage unless controlled by dusting or spraying. Guavas (Psidium spp.). — Guavas cannot be grown here except in very favorable localities. This plant is too sensitive to frost for its cul- ture to be attempted with any degree of certainty, and it is not recom- mended. Jujubes (Zizyphus jujuba). — Jujube culture is ideally suited to Im- perial Valley conditions. This tree is very hardy and succeeds on a va- riety of soils. It is deciduous and erect in habit of growth. Its bright- green leaves and red fruits make it attractive as an ornamental plant. The ripe fruits are eaten fresh, processed as candied fruit, or used in the manufacture of confections. It has but little commercial value, and prob- ably never will be important. Kumquats (Fortunella spp.). — Like guavas, kumquats are very sen- sitive to cold and must be protected even in this mild region. This is a citrus fruit, especially desirable for making preserves; or the fruit may be eaten fresh. It is not recommended for commercial planting, but may be grown in home gardens by those who will give it extra care. Lemons (Citrus limonia). — Lemons will probably never become com- mercially important in this region. They produce fairly well when given ample protection from wind and cold. They are also sensitive to the hot, dry climate, and are better adapted to more humid regions. Plantings should be confined to home gardens. Limes (Citrus aurantifolia). — Limes are more difficult to produce and more uncertain than are lemons. Plantings should be confined to experimental purposes and home gardens until more is learned of the possibilities of this fruit. Loganberries (Bubus loganobaccus). — Loganberries are not recom- mended except for home gardens. They are more difficult to grow in this section than are blackberries. Loquats (Eriobotrya japonica). — Loquats are small evergreen trees bearing long, broad leaves, and are suitable for ornamental plants. The fruits are valuable for making jellies. Loquat trees bloom very early and should be protected from frost. The fruit matures earlier than any other tree crop. They should be planted only for home use. Cm. 334] Soils and Crops of Imperial Valley 99 Mangos (Mangifera indica) . — Mangos are not adapted to this region and should not be planted except experimentally. Mulberries (Morns spp.). — Mulberries make good shade trees and are especially desirable for planting in poultry yards. They fruit heavily. Olives (Olea europaea). — Olives have been grown commercially here for many years, but the industry has at no time reached large propor- tions. This crop is very well suited to the climatic conditions, but has no special advantages over other sections where the industry has long been well established. Many varieties have been tested at the experiment station and else- where in this section. The varieties found best for pickling are the Mis- sion, Manzanilla, and Ascolano. Olives will thrive on a variety of soils, but planting on ditch banks and on land with a high water table should be avoided. Moderate irri- gation should be given. The young trees are very sensitive and should be protected to prevent sunburn. No insects or diseases attacking this crop have yet been reported in this region. Oranges (Citrus sinensis). — Oranges have been grown in home gar- dens here for many years, but not until recently were commercial plant- ings attempted. This industry, while promising, is yet too young for one to safely predict to what extent it can be developed. The culture for this crop is the same as that recommended for grapefruit. Peaches (Amygdalus persica). — Peaches have been grown experi- mentally and for home use since the early development of this region. Several varieties have been fairly productive, but it is very doubtful if the industry will ever develop into commercial proportions. A produc- tive variety of good shipping quality adapted to this region has not yet been discovered. However, this fruit should be included in all home- garden plantings. Pears (Pyrus communis). — Pears have been grown commercially for a number of years, and when given the best of care the crop has been very satisfactory. But no extensive development is expected, as the cli- matic conditions here are not favorable to the production of pears of the best quality, and direct competition must be met in marketing the fruit. Pear trees should be irrigated freely, and like other fruit trees in this section, they should be protected from sunburn. It is advisable to pro- vide for cross-pollination of pears. Pecans (Hicoria pecan). — Pecans, under certain very favorable con- ditions, have appeared promising in this section. However, more failures than successes with this crop have been recorded, and the soil should be selected with much care and understanding. Pecans are native to the 100 University of California — Experiment Station southern states, and the crop produces best there when grown on moist, alluvial soils, where the humidity is relatively high. To succeed in this region, the crop must be grown on deep, sandy or sandy loam soil that is practically free from alkali and rich in organic matter. In other words, the most choice land should be used to assure success with this crop. The wisdom of extensive plantings in this region is questionable at this time. Rather rapid developments of this crop have taken place in certain sec- tions of the southern states in recent years. Pecans grown in the Impe- rial Valley must necessarily come in direct competition with those grown on much cheaper land and at considerably lower cost of production. The life of the pecan tree is very long, and its development relatively slow. Full production cannot be expected in less than 15 or 20 years from date of planting, and then only with continuous good care. These facts should be very carefully considered by prospective growers before any planting is done. Western varieties are best adapted to this region and should be used to the exclusion of all others. The trees should have a plentiful sup- ply of water at all times, but their culture should not be attempted on land with a standing high water table. Varieties should be so arranged in the planting that cross-pollination will take place. Persimmons (Diospyros spp.) . — Persimmons of the American species have been a failure, but the Japanese varieties have done comparatively well. The Hachiya and Tanenashi varieties have produced fruit of very acceptable quality. The trees are extremely sensitive to sunburn and must be well protected. The crop is of no commercial importance in this section, but should be used in home plantings. Pineapples (Ananas sativus). — Pineapples are not suited to the cli- matic conditions and cannot be recommended. Plums (Prunus domestica). — Plums of the American and Japanese species have succeeded fairly well, but the European varieties of prunes should be avoided. Plum culture will probably never develop to any great extent, but plums should be grown for home use and for local and nearby markets. They do best when cross-pollinated, and varieties should be so arranged in the planting as to provide for this. Pomegranates (Punica granatum). — Pomegranates thrive in this region and produce heavily. The fruit is of exceptionally good quality, and is highly attractive. Pomegranates are easily propagated by cut- tings and are adapted to a variety of soils. They are also somewhat al- kali tolerant. This crop is grown commercially, but the market demands do not justify extensive plantings. The fruits are used more for decora- tive purposes, than for eating fresh. The moisture content of the soil should be kept as uniform as possible during the fruiting season to pre- vent splitting of the fruit. Cm. 334] Soils and Crops of Imperial Valley 101 H ^ Sat* &' 05 O ft- -2 X" 3 3 3 o o o K) «) 15 >> >> o o o o a ~ a "2 a .2 "9 .S "5 .5 .v. Z, -S ~ co o3 c3 M «2 » << J2 >>>>>>> fc^ M 3 S S 1-5 o o o o IN f» M - a^g i? eS o 9 5 o "3 *> to o o o o >»>.>>>>>> 00 00 00 -, £1 J2 „Q ,Q OJ O fa fa fa fa c c a a a III »— S I— 5 •— S •— = •— 3 § s 5 £ fa fa £ 05 QO 6 3 5 ■s-s § 03 c3 a O W cq ^ a O 03 PQ a o o o o o o o o fa Ph fa fa fa fa fa "0 13 TJ "O T) "d o o o o o o o o o o o o O O O O O O TJ T5 -d T3 .5 o o o o 03 C O O O fa O O O O 102 University of California — Experiment Station es 0> > 03 -a O ~ 2 S a ^ S O -ta o c "^ «5 ■** "^ H N H tH o o o e n » w cc „ 3 o 2 2 2 _; . ec ~h t-h <- 1 »-i - 1 --go a> u 3 s >' > > > o o o c 55 £ fc fc _o o o c •>J)«S){Jtio o5 00030 c ^ M Q ^ (si) M M 3 3 3 0 o3 Q o § 3 S & S* g* & §0^v5^OOC q3 3 ® C fe < Q ^ CD <]> OJ 3 3 3 3 3 3 w3 . •S s*^ o 03 o o> >« t» t^ i> O CN CN CN NN^ONiOlOu: o o o a-a^ CN CN CM - a> O t ^" ■* CT> o o c OO-HOSCOOOC ^ SO SO SO O^ O) Cj !>• rj< t* t* o o o^ o* 050>«DO'*r--r-t^ t-~ r- t^. t^ o o o O at -<*< -rp ■*< CO ^l -3 o> -T g ft Oh 3 j3 A o «5 urt ■c ifl >o >c "5 •c w. »a (-It-lb 3 3 3 MH ododcoaicooc S- Ei (H o, « d c *~! o> o> a. ^ Q Q C r? *h h h fe << << «! o o o c ^ o o c . • CN CN CN CN CN CN Q fefefefefefe a a a a r^ rv; r^ ^ ^ *< < 7,7.7, o o o o o o o 1 -^ o o c o ^ ^ ^ ^♦-'OOOOOC o o o c >.>>>> ffl _o d d c % 0> 0. C -^ -d ,£ ►2 fe fe fe fefei-s'-s'-:'-:'-:'-: & ,6 £l J2 ©004 fe fe fe fe 3 3 3 a a a 0) 2 T3 S3 s a o g >i ■u a > a a a -c a a X X if 1 s ^ O oc J Si '1 1 o ■3 (- o CO 1 S o> 3 -a li r > > t a > : P E i < > c 1 fe 1 a = c - >- r c L c I — > a a a s 0. PC 1 1 5 s X »■ "z ■r C % 5 1< p c ; c. 1 i I > I a E c c c g > PS S o _ O " If ■> o a > a c c K 1 P c 1 >> $ a < f. C -d T3 T3 T5 o o o o o o o o o .t O K '5 'S o .fe T3 T3 T3 T o o o c o o o c T3 T3 TJ t o o o c o o o c 5- '5 O O O O O f=H fe fe fefefefeOOOC OO O C fe fe fe a a o M o 2 ♦+ — CD V a. p, a 03 03 4 s a £ C Cj 0) oc 00 s c3 ad t- f- £ CD •'■ hi 01 c C h! t- h- fe s C C fe 8-» ^ CO "g 8 S 8 03 _0J _T « 2 8 fe s If 1 1 fe H Cm. 334] Soils and Crops of Imperial Valley 103 "(3 U5 «5 K5 O O a O a (O 0> « Q $ QQPQQ o o o o ■♦J +S +2+3 o o 5 o o >■ o o © a> as c fl i „ ^ -1 H O GJ 4> 5 3 3 ° ° ° lO lO lO i-H i-l .-H «-l CO i-H 5-2.2 o o O a> c3 03 fa "-» »"9 ,2-2-2 > be O 3 > > > > > o o o o o ^ >>>>>> o o a a a H w w «J «J 1> feSh o > > >> 0) O O S3 6B.JS - .S« *+> U S O D go's — o o o o o CO CO CO CO CO O O O 00 o o rl O O y t- < -*> o o o o o (M CM CM ^h co cc co §§ CM CM CM CM CM cp CD fa fa o o c a a c c 03 03 03 03 03 O O O O O O V o o o Q Q Q Q Q >> >> 03 03 3 3 fe fa fa -S -S "g g £ g fa fa fa A fc fe o o o e-^ o -^ o a a a a a a -g CJ « o ^ ^ ^ ^ ^ ^ OOO fa fa fa ^ 2 £ 03 4) £« c5 CO O 1 If -§ ft a a .2 t 3 ,2 c o e ^ 03 S WOW &&1 o (- a 5 c oj s g o o o o o o o o o o OOOOO fan E^ fafafaOOO »0 "0 'O OOO OOO OOO 'd *d ^ t* O O O O O O O O O O O fa fa O" 104 University of California — Experiment Station Quinces (Cydonia oblonga). — Quinces do comparatively well, pro- ducing large yields of excellent-quality fruit. They are not very exact- ing in the soil type required, and can be grown with a reasonable amount of care. They should be included in all home plantings. Raspberries (Rubus spp.). — Raspberries are not well adapted and should not be planted except experimentally. Strawberries (Frag aria spp.) . — Strawberries have been grown com- mercially in this region for many years, and they succeed well when properly handled. The management of this crop is rather difficult, and considerable skill and understanding on the part of the grower is re- quired. Sandy loam soils should be used and very frequent irrigations given. Fruit of good quality is produced, but earliness of maturity is the principal advantage held by this section. Only hardy varieties of proved value should be used. Some varieties are very sensitive to heat and will not endure the summers here. The accumulation of silt in the irrigation furrows has been one of the most serious problems in strawberry pro- duction. Tangerines (Citrus nobilis var. deliciosa). — Tangerines find a very congenial environment in this section, and have consistently yielded rather heavily. This crop requires the same cultural methods as de- scribed for grapefruit and oranges, but is more sensitive to poor soil and adverse conditions. Youngberries (Rub us sp.) . — Youngberries, like loganberries, are not very well suited to the climatic conditions of this region, and commercial plantings are not recommended. ORNAMENTAL PLANTS Shade trees are vital to the comfort of man and beast in this region, and ornamental plants are a very desirable attribute. Although experimen- tal work on ornamentals has been limited, it is believed that the follow- ing plants are suitable for the several purposes for which they have been listed : Shade and Ornamental Trees Acacia melanoxylon (blackwood acacia) Eucalyptus rostrata (red gum) Casuarina stricta (beef wood) Eucalyptus rudis (desert gum) Ceratonia siliqua (carob) Cercidium torreyanum (palo verde) Citrus grandis (grapefruit or pomelo) Cupressus arizonica (Arizona cypress) Cupressussempervirens ( Italian cypress) Eucalyptus sideroxylon var. rosea (red Erioootrya japonica (loquat) rronbark) Eucalyptus creora (narrow-leaved iron- Fraxinus velutina (Arizona ash) bark) Hicoria pecan (pecan) Eucalyptus tereticornis (gray or slaty gum) Eucalyptus viminalis (manna gum) Cm. 334] Soils and Crops of Imperial Valley 105 Shade and Ornamental Trees — ( Continued) Koelreuteria paniculata (goldenrain tree) Melia azedarach var. umbraculiformis (Texas umbrella tree) Morus nigra (black mulberry) Olea europaea (common olive) ParMnsonia aculeata (Jerusalem thorn) Phoenix dactylifera (date palm) Pinus halepensis (Aleppo pine) Pistacia chinensis (Chinese pistache) Prosopis juliflora var. glandulosa (honey mesquite) Prunus cerasifera var. pissardi (purple- leaved plum) Salix babylonica (Babylon weeping wil- low) Salix laevigata (red willow) Schinus molle (California pepper tree) Sterculia diver sifolia (Australian bottle tree) Tamarix articulata (athel tree) Thuja orientalis (Chinese arbor vitae) Ulmus pumila (Chinese elm) Washingtonia filifera (Washington fan palm) ; and other palms in variety Zizyphus jujuba (Chinese jujube) Shrubs Acacia armata (kangaroo thorn) Acacia longifolia (Sydney wattle) Berberis thunbergii (Japanese bar- berry) Cactus (cactus in variety) Callistemon (bottlebrush) Cotoneaster spp. (for ornamental ber- ries) Cytisus (broom or genista) Cydonia japonica (Japanese quince) Fremontia mexicana Lagerstroemia indica (crape myrtle) Lavatera assurgentiflora (California tree-mallow) Leptospermum laevigatum (Australian tea-tree) Ligustrum (privet) Lippia citriodora (lemon verbena) Myrtus communis (true myrtle) Nerium oleander (oleander) Plumbago capensis (cape plumbago) Prunus ilici folia (hollyleaf cherry) Punica granatum (var. Wonderful pomegranate) Eicinus communis (castor bean) Rosa (rose) ; varieties as follows: Eed Radiance and Pink Radiance Los Angeles, pink with buff shades Harry Kirk, yellow Golden Emblem, yellow and orange Madame Abel Chataney, pink with orange Mrs. Chas. Bell, palest pink Hoosier Beauty, deep red Hadley, deep red Mrs. W. E. Egan, deep pink Tamarix parvi flora (tamarix, pink) Yucca (yucca in variety) Ampelopsis quinquefolia (Virginia creeper) Antigonon leptopus (coral vine, or rosa de-montana) Bignonia grandiflora (Chinese trumpet- creeper) Bignonia unguis-cati (trumpet vine) Calonyction (moonflower) Cardiospermum halicacabum (balloon- vine) Climbing Plants and Vines Ficus pumila (climbing fig) Ipomoea purpurea (Japanese morning- glory, annual) Jasminum primulinum (primrose jasmine) Lantana sellowiana (trailing lantana) Lathy rus latifolius (perennial sweet pea) Lathy rus odoratus (sweet pea, annual) 106 University of California — Experiment Station Climbing Plants and Vines— (Co ntinued) Lonicera japonica var. halliana (Hall's honeysuckle) Parthenocissus tricuspidata (Japanese or Boston ivy) Phaseolus coccineus (scarlet runner, annual) Rosa (climbing rose, var. Cecil Brunner) Thunder gia (thunbergia) Tropaeolum peregrinum (canary-bird vine) Vitis (grape, var. Thompson Seedless or Sultanina) Vitis arizonica (canyon grape) Wisteria sinensis (Chinese wisteria) Flowe*rs for Beds or Masses Ageratum (floss flower) Alyssum maritimum (sweet alyssum) Antirrhinum (snapdragon) Arctotis grandis (African blue daisy) Aster (aster) Calendula officinalis (pot marigold) Canna (canna) Celosia argentia (feather cockscomb) Chrysanthemum maximum (Shasta daisy) Chrysanthemum mori folium (chrysan- themum) Delphinium ajacis (larkspur) Dianthus barbatus (sweet william) Dianthus caryophyllus (carnation) Dimorphotheca aurantiaca (winter cape marigold) Eschscholtzia calif ornica (California poppy) Gaillardia (gaillardia) Godetia (godetia) Iberis amara (candytuft) Iris (iris) Lathyrus odoratus (sweet pea) Linum (flax) Myosotis (forget-me-not) Petunia (petunia) Phlox (phlox) Portulaca (portulaca) Reseda odorata (mignonette) Salvia (flowering sage) Tropaeolum ma jus (nasturtium) Verbena (verbena) Viola odorata (sweet violet) Viola tricolor (pansy) Zinnia (zinnia) Althaea rosea (hollyhock) Centaurea cyanus (cornflower) Cheiranthus cheiri (wallflower) Cosmos (cosmos) Dahlia (dahlia) Datura (datura) Other Flowers for Open Planting Helianthus annuus (sunflower) Impatiens (balsam) Kochia scoparia (summer cypress) Lupinus (lupine) Mathiola (stocks) Annual and Perennial Flowers for Shade or Partial Shade Linum (flax) Nemesia (nemesia) Antirrhinum (snapdragon) Arctotis grandis (African blue daisy) Begonia (begonia) Bellis perennis (English daisy) Clarkia (clarkia) Delphinium ajacis (larkspur) Godetia (godetia) Iberis amara (candytuft) Nemophila insignis (baby blue-eyes) Nigella damascana (love-in-a-mist) Rudbeckia (coneflower) Viola odorata (sweet violet) Viola tricolor (pansy) Cm. 334] Soils and Crops of Imperial Valley 107 WINDBREAKS Windbreaks are very desirable in this general area for various purposes. They are probably most valuable in protecting fruits, especially citrus fruits, dates, and grapes. They are also valuable in protecting dwell- ings, poultry yards, and home gardens. When windbreaks are to be used, their planting and care should be carefully planned and executed. The most serious objection to the exten- sive use of windbreaks is that they rob the cultivated crops of both plant foods and moisture. This objection can be partially overcome by allowing a liberal distance between the windbreak and the first culti- vated row. A space 50 feet or more wide should be wholly devoted to the windbreak. As the windbreak is planted on the west side of the crop to be protected, the roots should be encouraged to develop on that side in order to relieve competition with the cultivated crop. This can be done by applying liberal irrigations and possibly fertilizers on that side of the windbreak row. A few feet from the windbreak row on the east side, a subsoiler should be run at least twice each year, to prevent any shallow root development in the feeding zone of the cultivated crop. Ample room should be provided between the windbreak and the first cultivated row to allow the easy operation of tractor and subsoiler. When the wind- break gets to be large it should be irrigated heavily, preferably by a series of basins. The most widely used windbreak tree in this section is the athel (Tamarix articulate) . It is propagated by cuttings and makes a very rapid and dense growth if given an abundance of water. Unless given the best of care as described above, athel windbreaks will rob the soil over a wide area. Several varieties of eucalyptus also make desirable windbreak trees. The red gum (Eucalyptus rostrata), the gray or slaty eucalyptus (E. tereticornia) , and the desert gum (E. rudis) are probably the best for this purpose. Close spacing of trees is necessary for the most effective protection. Areas from three to five times as wide as the height of the windbreak will be protected. The eucalyptus makes a higher wind- break than any other tree used here. The beef wood (Casuarina stricta) and the Australian pine or horse-tail tree (C. equisetifolia) , while not forming as dense windbreak as some other trees, offer promise of less root competition, and are recommended for trial. They should prefer- ably be planted in double rows. 108 University of California — Experiment Station ACKNOWLEDGMENTS The writers desire to express their appreciation of the assistance ren- dered by a large number of persons who supplied information or who made available certain data incorporated in this circular. Special acknowledgment is due to Dr. John P. Conrad, who compiled much of the experimental crop data recorded at the Imperial Valley Experiment Station; to Mr. M. J. Dowd, Chief Engineer and General Manager of the Imperial Irrigation District; to Mr. F. G. Beyschlag, Farm Advisor of Imperial County; and to Mr. B. A. Harrigan, Agri- cultural Commissioner of Imperial County. 15m-8,'34