UNIVERSITY OF CALIFORNIA COLLEGE OF AGRICULTURE AGRICULTURAL EXPERIMENT STATION BERKELEY, CALIFORNIA Studies Preliminary to the Establishment of a Series of Fertilizer Trials in a Bearing Citrus Grove L. D. BATCHELOR, E. R. PARKER, and ROBERT McBRIDE BULLETIN 451 APRIL, 1928 UNIVERSITY OF CALIFORNIA PRINTING OFFICE BERKELEY, CALIFORNIA 1928 STUDIES PRELIMINARY TO THE ESTABLISHMENT OF A SERIES OF FERTILIZER TRIALS IN A BEARING CITRUS GROVE 1 L. D. BATCHELOE2 E. R. PARKER 3 and ROBERT McBBIDE* INTRODUCTION Many fertilizer and cultural trials which have been reported upon have been conducted under the implied assumption that the land on which the trials were located was 'uniform.' However, it has been evident to students of soil fertility during the last two decades, that, in reality, the productivity of the soil varies greatly in different sec- tions of an experimental field. In some instances this variability of the soil has masked the effect of fertilizer trials to such a degree that the observed results have been very misleading. Fertilizer trials conducted on land which has not been subject to previous study regarding its relative productivity for the crop to be experimented with must ordinarily be considered subject to large experimental errors. It is not sufficient to test the variability of land with one crop and then experiment with another. This point has been clearly demonstrated with many crops. It is now apparent with oranges on the Rubidoux experimental plots of the Citrus Experi- ment Station. Here such soil variations have been created by twenty years of differential fertilizer trials that there are very radical differ- ences in the growth and production of orange and lemon trees on the several plots. Clover cover crops, however, have grown almost equally well on land which has not been fertilized for twenty years, and on plots which have received liberal applications of 'complete' fertilizer for the same period of time. The present study, preliminary to the establishment of a rather large-scale fertilizer trial in a bearing orange grove, is the natural 1 Paper No. 178, University of California, Graduate School of Tropical Agriculture and Citrus Experiment Station, Riverside, California. a Professor of Orchard Management in the Citrus Experiment Station and Graduate School of Tropical Agriculture, and Horticulturist in the Experiment Station. a Assistant in Orchard Management, Citrus Experiment Station. * Assistant Superintendent of Cultivations, Citrus Experiment Station; died February 1, 1927. 4 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION outgrowth of the attempt to profit by the advances which have been made during the past two decades in the methods of conducting field trials. Such advances have resulted from the studies of many investi- gators both in this country and abroad. These have been freely drawn upon as a guide in these studies. The paper here presented is principally a general progress report in the nature of a popular dis- cussion. A more strictly statistical analysis of the data well be pre- pared for publication in the near future. The use of fertilizer material is practically a universal necessity of citrus culture in all parts of the world, and particularly in Cali- fornia. The per-acre charge for fertilizer materials in this state will vary from a few dollars to, in some cases, more than one hundred dollars a year. Any study which will give additional knowledge regarding the most effective and economical use of fertilizers, and provide a means by which the effects of various materials upon the soil may be studied, is of paramount interest to those engaged in the culture of citrus fruit in California. Many difficulties are encountered in obtaining a satisfactory orchard to be used for a complex field trial. Commercial orchards are usually much too variable to use for experimental purposes. They are usually located upon land of uncertain history. They may be growing on land a portion of which has receiver a fertilizer treatment in the past which will create a difference in productivity of the soil, persistent over many years. The trees themselves may be subject to great inherent variability of size, vigor, and productivity. It has been demonstrated by several investigators that the rootstock has a great effect on the growth of the trees, at least during their early history. Because of these conditions a commercial grove may be entirely unsuited to experimental use. Other observations indicate that variations in certain characters of the top may be avoided by careful selection of bud wood. The general planting plan, also, of an experimental orchard may vary from that ordinarily employed in a commercial planting. Careful planning of an experimental planting may decrease the effort required in maintaining it, as compared with a commercial orchard adapted to the purpose. It also may facilitate the reduction of the experimental error by making possible the appli- cation of recognized methods of plot-trial technic. The final value of the use of different fertilizer materials may not be fully established until they have been applied to the same plots for many years. The trials herein discussed may therefore be expected to continue for a period of twenty or thirty years. In consideration of BuL. 451] FERTILIZER TRIALS IN A BEARING CITRUS GROVE 5 all of these facts it is desirable to carry on such trials upon publicly owned property. In this case change in ownership will not necessi- tate the modification or discontinuation of experiments which may, if continued, be productive of additional useful information. In view of the foregoing comments it appeared necessary in 1914 that an orchard be established for the specific purpose of using it for fertilizer trials. The orchard described herein was planned in an effort to make it as satisfactory as possible for this use. HISTORY OF LAND AND ESTABLISHMENT OF THE GROVE, INCLUDING PROPAGATION AND CULTURE GENEEAL HISTORY AND DESCRIPTION OF THE LAND The establishment of the fertilizer trials herein discussed was one of the recognized objectives of the Citrus Experiment Station when a new site was purchased in the year 1914. The land chosen for planting the experimental grove was selected largely because of the apparent uniformity of the soil, and of the past cultural practices. Thus it was deemed particularly suitable for the purpose of conduct- ing the trials under consideration. It seems desirable at this time to discuss somewhat in detail the history and the cultural treatment of the land during the periods preceding and following the planting of the trees, and especially during the latter period. The soil is classified as Ramona loam by the United States Depart- ment of Agriculture soil survey. 5 The land was first cleared in 1875 and planted to grain in 1876. From this date until the purchase of the land by the state in 1914 it was sown annually to barley or wheat, with the exception of an occasional year during which the soil was left fallow. The land slopes gradually toward the west, with an average grade of 1% per cent. No systematic effort to grade or level the land was made during the time it was cropped to grain, so far as is known. The ordinary plowing and harrowing, however, would fill in the small depressions which normally occur in newly cleared land, and doubt- less the land presented a much smoother general aspect at the time of s The soil is of old alluvial origin. It is derived from granite rock, and contains some mica. The soil to a depth of about 12 inches consists of a rather friable, light-textured, gritty loam of brown color. It is very slightly reddish brown when wet. The substratum is a compact gritty loam of greatly varying thickness; occasionally it extends to a depth of only 4 feet from the surface, but rarely extends to 20 feet from the surface. Below this formation the lower strata become gradually so compact that they can be penetrated only with great difficulty. b UNIVERSITY OF CALIFORNIA EXPERIMENT STATION purchase in 1914, after thirty-eight years of dry farming, than it did when the brush was first cleared from the land in 1875. This natural filling in of depressions and the lowering of the higher local areas of soil, which would unavoidably occur during nearly four decades of farming, may in a measure account for some of the marked differences in productivity between small adjacent areas, which will be more fully discussed later. The surface was sufficiently smooth in 1914 so that only a very slight amount of grading of the surface soil was necessary in prepar- ing the land for irrigation. This grading was done only on the west edge of the field. The irrigation system was installed during the spring of 1917 and the land was irrigated for the first time during May and June of that year. Figure 1 shows the shape of the field and the arrangement of the experimental plots. THE PEOPAGATION OF THE TREES Selection in the Nursery. — It was recognized in planning the experiment that one of the requisites for the accuracy of the future experiments was to secure uncommonly uniform nursery trees. This is essential in order that the trees in all future plots will be as nearly equal as possible in size and yielding capacity. Extra care, beyond that used in the ordinary commercial production of trees, has been exercised to effect a reduction of differences between trees. Varia- tions which might be inherent either in the rootstocks used or in the parent trees from which buds were taken have both been considered in the nursery. The following measures were followed to produced especially uniform trees : 1. The sweet orange (Citrus sinensis) nursery stock which was transplanted from the seed bed to the nursery in 1914, was thoroughly culled and the undersized trees were discarded. These discards amounted to possibly 15 per cent of the seedlings. 2. After one year's growth in the nursery, and at the time the 1 rees were budded in 1915, another selection of the small-sized trees was made, and these were discarded. :>. When the trees were dug from the nursery for transplanting to the grove in 1917, the small-sized budded trees were culled from the lot, making a third discarding of trees which lacked vigor and size. Thus from the establishment of the nursery until the actual planting of the grove, an endeavor was continuously made to produce a vigorous and unusually uniform lot of trees. BuL. 451 J FERTILIZER TRIALS IN A BEARING CITRUS GROVE 7 B/oCh D f r G // /v < 1 m s yv J /r n Z 4 6 8 10 /2 n /z /4 it 20 22 22 24 24 28 30 U 2d 34 3^ 38 42+4 H Fig. 1. — Plan of experimental field, showing arrangement of blocks and plots. 8 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION Selection of Buds — Plump, well-formed buds from mature bud wood were used for propagation purposes. Only such twigs were used as showed blossoms formed or in process of formation on the tips of the current season's growth at the time the bud wood was cut. The Washington Navel orange trees that are to form the experi- mental rows were propagated from trees for which yield records had been kept for several years. Only the heavy-producing trees were used as a source of bud wood. The grapefruit trees were propagated from high-yielding parent trees of recorded performance. The Valencia bud wood, on the other hand, came from trees which were true to type, but not from performance-record trees. PEEPAEING THE LAND The actual preparation of the land for tree planting began during the fall and early winter of 1915. The land was deeply plowed at that time; part of the area was dry-plowed with a disk plow in the fall and the remainder was plowed with a moldboard plow after the rainy season began. The main portion of the field, that west of the canal lay in a rough fallow condition until the summer of 1916, when it was again plowed. This latter plowing was not deep and was done primarily to kill the weed growth. . The small portion of the field east of the canal (12.7 acres), as shown by figure 1, was not prepared exactly as heretofore noted for the main portion of the field. A crop of oat hay was produced on this area during the spring of 1916. The land was then left in grain stubble until tree planting began in the spring of 1917. PLANTING THE TEEES During the spring of 1917, a narrow strip of land was plowed where each future tree row was to be located. The tree holes, 24 inches deep and 24 inches in diameter, were dug early in May. A pre- liminary soil survey was made by making a hole 4 feet deep from the surface of the ground with a soil tube, in each hole which was dug for tree planting. Slightly less than 10 per cent of the holes, that showed a semi-impervious layer within 4 feet of the surface of the ground were blasted. Before the actual planting began, the surface soil was filled back into the holes to a depth of 12 inches from the surface. The soil was then settled by irrigating the rows of holes before planting the trees. After the trees were planted, they were thoroughly irrigated to settle the soil around the roots. 5 7. BUL. 451] FERTILIZER TRIALS IN A BEARING CITRUS GROVE 9 The entire orchard was planted in pairs of blocks each ten trees deep. Separate irrigation lines were ultimately laid for each of these blocks, so that each block of trees may be irrigated separately. The Washington Navel orange trees were planted as the test variety. Each alternate row constitutes an experimental plot and contains eight trees of this variety. The first tree of each test row, next to the pipe 7>,*>* <.,», /. __Z. _J. _?. _S. _§. _f. _fl. _9. _J?. _!/■ _J2- _J?: _L+. """"" ,0 © © © © © © © © © '000000000000 "^" *© © © © © © © © © '000000000000 I*© ©0000 ©.©000© 5 !«-0©0©©©0©0©0© ©0®0©©©0©0©0 •©00000000000 '■000000000000 '•000 ©000 ©000© •0 0© 00 0© ©00 0© -©©0000000000 1.000000000000 : ^-000000000000 5 jj <©©©©©©©©©©©© Fig. 2. — Showing arrangement of trees in plots and guard rows. line, however, is a Valencia orange tree and the tenth tree is a grape- fruit tree. The rows alternating with the test rows are planted throughout the orchard to Valencia and grapefruit trees alternating. These latter rows will be considered guard rows between the fertilizer plots and are designed to prevent to some extent the overlapping of the effects of different fertilizer treatments from one Navel roAV to another. The plan of planting may be more clearly understood by reference to figure 2, which shows portions of two blocks of the experimental field. rc& BLOC* £ 10 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION INTERCROPPING THE GROVE DURING THE SUMMER SEASONS OF THE FIRST FOUR YEARS The land between the tree rows remained in a fallow condition during' the planting operations. As soon as the trees were set, this space was prepared for planting beans, The beans were planted in rows 36 inches apart with six rows of beans in each interspace between the orange tree rows. During the first four years of the existence of the grove it was inter-cropped each summer to Blackeye beans (Vigna sinensis) and planted to a bitter clover (Melilotus indica) cover crop each fall. The winter cover crop was planted in September and plowed under during the following February or March. Figure 3 shows a view of a portion of the experimental field during the first year, before the harvest of the bean crop. The yearly intercropping of the land to Blackeye beans for four years furnished considerable straw to apply as a fertilizer material to the young trees. This bean straw was applied in deep furrows. The first year a furrow was made with a large moldboard plow on each side of the tree rows at a distance of 2% feet from the trees. The bean straw was buried in the furrows on two sides of the trees, distributed along a space of 3 or 4 feet in the furrow. An average of 20 pounds of bean straw per tree was applied. During the fall of the second year (1918) all the bean straw pro- duced as an inter-crop and also about ten tons produced on nearby fields, was applied in furrows to the 48 acres of the experimental field. The furrows were made parallel to the tree rows, placed about one foot further away from the trees than the furrows of the 1917 season. In addition to this, one furrow on each side of the trees was made across the tree rows, at a distance of 4 feet from the tree trunk. All the furrows were made about 12 inches deep. The straw was applied at the rate of 24 pounds per tree. Figure 4 shows the method of applying the straw along the tree rows during the second year. It was trampeled down, and then covered over by using a moldboard plow. An examination of this straw in January, 1919, showed that the straw was covered with an average of 5 inches of soil. During the early fall of 1919 furrows were again made parallel to the tree rows one foot further away from the rows than the pre- vious year, making a total of 4^ feet and straw was applied at the rate of 17 pounds per tree. BuL. 451] FERTILIZER TRIALS IN A BEARING CITRUS GROVE 11 Fig. 3. — View of part of the experimental orchard, looking in southwestern direction, during the first year (1917). The summer inter-crop between the tree rows may be seen. Fig. 4. — Method of applying bean straw in furrows during second year (1918). 12 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION The orchard was intercropped to Blackeye beans during the sum- mer of 1920 for the last time. After the bean harvest of that year the straw was applied in furrows made across the tree rows and so placed that they were about one foot from the cross furrows made in 1918 and thus approximately 5 feet from the tree trunks. Ten pounds of straw was applied per tree ; only 75 per cent of this straw had been produced as an intercrop, the remainder having been grown on nearby land. >^>; w * Fig. 5\ — Summer cover crop of Whippoorwill cowpeas, 1921. CULTURE OF THE GROVE DURING SUMMER SEASONS OF FIFTH TO NINTH YEARS, INCLUSIVE In both 1921 and 1922, summer cover crops of Whippoorwill cow- peas (Vigna sinensis) were grown. The cowpeas were planted in lows and cultivated during the interval between irrigations until the growth of their tops made this operation no longer practicable. They were planted in May and disked under about the middle of August with a double disk and tractor power. A relatively heavy production was secured each year. The green weight of the crop for 1921 was 10.5 tons to a solid acre of cowpeas, and for 1922 it was 13.8 tons. Although the cowpeas were planted in the tree rows in 1921, the irri- gation water did not reach them well and the crop there was stunted. BUL. 451J FERTILIZER TRIALS IN A HEARING CITRUS GROVE 13 For this reason only three-quarters of the land was really productive of a cover crop that year. During the 1922 season, however, per- manent irrigation furrows were made in the form of a figure eight between each two trees in the tree rows. This method of irrigation produced as good tonnage of cowpeas in the tree rows as in the inter- spaces, and all the land except that actually under the trees produced a summer cover crop. The appearance of the grove and the summer cover crop in 1921 is well illustrated by figure 5. WINTEE COVER-CROPPING Throughout the entire history of the grove with the exception of 1926-27, a cover crop has been grown during the winter seasons. Yellow bitter clover (M. inclica) has been used every year except 1923-24 when purple vetch (V. at ro purpurea) was used. A good commercial tonnage of winter cover crop has been grown six years out of nine. During the spring of 1922 and also of 1923 the tonnage plowed under was very light, owing to the destruction during the previous fall months of many of the young clover plants by the alfalfa caterpillar (Eurymus eurytheme) . The crop of purple vetch plowed under in 1924 was also relatively light because of the ravages of the destructive pea aphis (Macrosiplium pisi), which greatly reduced the growth of the crop the last two weeks before it was plowed under. The average annual jdeld was about 11 tons of green weight to a solid acre of cover crop. The approximate average green weight per acre was 13 tons in 1925 and 11 tons in 1926. During the years when Blaekeye beans were grown as an inter- crop, the winter cover crop was sown as early as possible after the bean harvest, which was usually the latter part of September or early October. It was then plowed under by the middle of March. This gave plenty of time for the green material to decompose and the land to be prepared for bean planting. Since the fall of 1921 the winter cover crop has been planted earlier than heretofore, usually about the last week in August or the first week in September. The crops have been plowed under during the last ten days in February for the last five years. Throughout the whole life of the grove the winter cover crop has been plowed under to a depth of from 9 to 10 inches with a moldboard plow and tractor power. During the summer seasons of 1923 to 1926, inclusive, clean cul- ture was practiced. The first two years of this period the soil was worked two or three times during the time intervening between two irrigations. The usual practice was to harrow over the grove with a 14 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION spike-tooth harrow as soon as the land was sufficiently dried out after an irrigation. It was then cultivated both with the tree rows and crosswise, with a heavy cultivator drawn by a tractor. This program of cultivation for the summer months was judged to be excessive, and was modified beginning with the summer of 1925. During the last three summers the irrigation furrows have been allowed to become thoroughly dry without being ' pulled in ' by the use of a harrow. The land has been merely cultivated, ordinarily only one way, with a heavy cultivator, between irrigations. The land has been thoroughly dry, so that some clods have been formed by the cultivation. The furrows for the next irrigation have been made approximately one week after cultivation and have been allowed to remain open for a week or ten days before irrigation. The modification of the cultural practice by reducing the number of cultivations between irrigations has been followed by a marked improvement in the readiness with which the soil has absorbed irrigation water. IREIGATION PRACTICE The irrigation practice followed has been in general similar to that employed under commercial management of like properties of the district. The nature of the soil and the slope of the land has made it advisable to use the furrow method of irrigation exclusively. From 2% to 4 acre inches of water per acre has been the usual single appli- cation. During the years when intercrops or summer cover-crops were grown between the tree rows the land was irrigated in accord- ance with the demands of the annual crop, with the exception that one furrow on each side of the young trees was used to give them water at frequent intervals, regardless of the needs of the intercrop. The time of irrigation of the grove and cover crops has always been determined by the moisture content of the soil. This has ordi- narily been accomplished by the frequent use of a soil tube in various parts of the field. In addition, beginning with the year 1922, a record has been kept of the moisture content of the soil, in plots distributed at random throughout the field. When only the needs of the trees have been considered the average interval between irrigations during the summer months has been from twenty-five to thirty days. The winter cover crops have been irrigated at frequent intervals during the fall months. The usual absence of rains during the period From September to November, inclusive, has made it advisable during most years to apply a light irrigation every fourteen to twenty-one Buu451] FERTILIZER TRIALS IN A BEARING CITRUS GROVE 15 days in order to keep up a continuous growth of the young cover- crop plants. The total amount of water applied annually has varied from 30 to 48 acre inches per acre, according to the rainfall and the needs of the intercrops. One notable objection to the growing of a summer cover crop of cowpeas has been the lack of penetration of the irrigation water, when it is necessary to run water time after time in the same irrigation furrows. During the latter part of the growth of the cover crop, 225 cvix#ocvj^;vaa>oc\j.^ir>c9oc\j^voa>ot\i <* •HrHiHr-lrHCVlCMCMCM tOtOtOnW^-J3 FLOT NUMBERS Fig. 6. — Average yield per tree in each plot of Block I, for each of six years, 1922 to 1927, inclusive. from July 15 to August 15, it has been practically impossible to wet the soil below 2 feet from the surface. This system of culture may be seriously objected to on the Ramona loam soil, and similar soil types, because of the lack of penetration of the irrigation water. The maximum demand of the intercrop for water comes at a time when the midsummer demand of the fruit-laden trees is also high. It has been literally impossible to apply sufficient water for both crops on the soil types here encountered. Allowing the water to run 24 hours per irrigation it was impossible to apply more than 0.8 to 1.0 acre inch per acre. With a 48-hour run usually less than 2.0 acre 16 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION inches per acre could be applied. Running water continuously for 48 to 72 hours did not accomplish a satisfactory irrigation. Under such conditions it has been necessary to apply water every seven to ten days and even then the very small amount taken up by the soil was insufficient for the best development of the young trees. The results of the two years of summer cropping to Whippoorwill cowpeas in this orchard have shown clearly that practically no sum- mer growth of the trees took place from June to August, inclusive. JlllIIBBB - = = p : — 5^S; s; 1 "zh^-h^^U 1 ^j^T "l kl c ^3J~~ Sl N_i' [ — h"" — \--& ^S 5 »B S; - "IS 2 & j-f- "^t 2 -- , "t"S^-_L — L- r>4j | (tV ***i ~""r"~" ■' """M^i ' i Ny / ' S> » .... """^S*"^ i ==^=::-V ^,1926 _ lisSlIIi: _ :-f-s s ___j — O ^vJ 1 § » llllllll jlllllllllllll illfllll !■ 70 ^_*5*_ 5*.„^ TH^T z ~~ s— V 1— 1 1 1 :Eeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee|ee_ee|eeeeeee|eee >EFGHIJKLM BLOCKS -Average yield per tree in each block, for each of six years, 1922 to 1927, inclusive. A month after the cover crop was disked under, or about September 15, growth started on the trees and became exceedingly great by October 15 to November 1. The frost hazard naturally became much greater under such conditions than when the trees made three or four normal cycles of growth during the growing season and entered the autumn period in a well-matured condition. The practices which have been pursued in the development and culture of this orchard have resulted in the production of a very satisfactory property from a commercial viewpoint. The size and BuL. 451] FERTILIZER TRIALS IN A BEARING CITRUS GROVE 17 productivity which the trees have attained, especially during the first six-year period, have been somewhat greater than that usually reached during the same interval of time on similar properties. TABLE 1 Average YrELD Per Tree in each Plot of Block I, for each of Six Years, 1922 to 1927, Inclusive Plot Year lfi 20 22 24 2li 28 30 32 34 36 38 40 42 Average yield per tree, in po unds 1922 90 112 123 104 91 85 75 83 87 85 105 82 93 88 114 78 68 117 87 90 93 83 1923 63 62 79 68 55 55 51 75 60 68 86 86 64 75 103 81 69 104 88 82 86 58 1924 149 145 162 171 146 151 143 153 156 165 183 158 147 172 196 162 142 186 172 175 177 153 1925 145 151 171 164 145 141 131 123 135 135 153 116 116 149 155 140 134 158 152 171 157 140 1926 103 106 119 107 126 113 101 106 116 127 136 93 95 117 151 117 128 132 141 144 146 139 1927 128 144 183 157 168 132 146 140 164 167 163 154 186 172 193 178 187 203 177 187 204 181 Avg. 113 120 140 129 122 113 108 113 120 125 138 115 117 129 152 126 121 150 136 142 144 126 It is believed that the practice of growing leguminous intercrops has been of distinct advantage in improving and maintaining the yields of this orchard. The appearance of the trees and the yields now indicate, however, that the growing of winter cover crops as practiced and without the use of fertilizer material is not maintaining the trees in a condition of greatest vigor. As indicated in figures 6 and 7 and also in table 1, the yields of the trees have not been increased since 1924 until the year 1927. Although the latter was an exceptionally good year for orange production in this district, only a slight increase over the yield of 1924 was recorded. The present appearance of the trees also shows that they are not in a condition of luxuriant growth. In comparison with well-fertilized orchards in the vicinity, the new growth appearing on the Navel orange trees during the 1925-1926 season in this orchard was slight and small-leaved. This, is illustrated by figure 8, which shows a tree of the average size and production for the entire field, photographed in 1927. At the end of the ten-year period it is believed that some nutrient materials are present in the soil in such low concentrations that they are beginning to limit the growth and productivity of the trees. This condition makes the present, therefore, an ideal time to commence the differential treatments, since a relatively early response to beneficial treatments may be anticipated. 18 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION OBSERVATIONS REGARDING THE VARIATION IN THE SIZE AND PRODUCTIVITY OF THE TREES TEUNK MEASUREMENTS Records have been made annually of the growth of the trees. Trunk-circumference measurements have been made during the whole period since the trees were planted. The yearly trunk measurements have been at the same position on the trunk. Each tree has been marked with a painted band showing the place of measurement. The smallest circumference on the trunk between the swell of the branches and the swell of the root system was chosen for this measurement. This measurement was converted into area of cross section. Space will not permit presenting all the data which show the amount of variation among all the individual trees for each year. However, an illustration of the amount of variation in the plots is shown by table 2, which presents the average trunk size per tree, in each plot, in 1926. TABLE 2 Average Trunk Measurement pfr Tree in each Plot for 1926 Block Plot M L K 1 J I H G F E D A rea of cros s section in square centimete rs 2 111 109 104 117 129 132 134 4 111 114 112 105 129 134 142 6 118 114 113 107 128 121 127 8 119 113 109 129 133 130 139 10 115 120 127 123 141 135 136 12 113 125 122 117 130 135 129 14 126 121 137 120 146 153 132 128 16 122 122 131 120 135 148 103 114 18 122 117 120 127 149 136 133 131 20 115 115 126 127 143 142 128 126 22 129 122 133 127 134 140 140 129 127 24 132 * 127 124 129 137 133 118 125 26 124 126 117 131 137 128 129 128 28 127 122 141 127 123 127 134 128 30 128 121 133 139 132 127 130 137 32 120 119 128 126 138 122 129 144 132 34 114 * 135 119 139 132 135 124 125 36 122 119 133 123 133 136 137 132 126 38 107 117 114 123 122 128 136 122 125 40 128 118 134 124 118 123 126 123 130 42 118 110 120 118 136 123 131 132 128 44 112 121 132 130 113 115 127 131 133 46 118 134 147 139 48 127 132 125 126 50 131 128 128 137 52 129 134 143 138 54 135 142 * 131 * Plots omitted because of injury to frees. Bul. 451 FERTILIZER TRIALS IN A BEARING CITRUS GROVE 19 In averaging the eight trees of a plot, the variation in the individual trees has naturally been leveled to some extent. On the basis of the mean size of the trees in each plot, the differences are greater than would be expected, when the care spent in establishing a uniform grove is taken into consideration. Fig. 8. — Individual Navel orange tree of average size and production at time of starting the fertilizer trials, 1927. (Tree E-4-3.) The trees in plot E-16 are among the smallest in trunk cross- section ; those in plot H-14 are 49 per cent larger. The measurements of the trees in these plots in 1918, one year after the trees were planted in the orchard, showed that plot H-14 was even then 31 per cent larger than plot E-16. Apparently the chance distribution of the trees at the time the orchard was planted accounts in a large degree for subnormal-sized trees being originally grouped together in plot E-16. In addition to this, the fact that this plot has been making slower growth than 20 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION some of the other plots leads us to conclude that E-16 is also located on soil which is subnormal in productivity in comparison with many other plots of the field. It seems probable that the present range in plot averages of tree size could have been materially reduced by so distributing the different-sized trees at the time of planting as to make the plot aver- ages uniform throughout the field. The distribution of the trees by pure chance might be expected to locate a group of either exception- ally large or exceptionally small trees in the same plot occasionally. VOLUME OF TOPS Top-volume measurements have been made yearly since 1921, and have been recorded in cubic feet. The measurements over and around the trees have been taken to the nearest foot by means of a fumigation tent, and the cubic contents calculated by the conventional method used in determining fumigation dosage. TABLE 3 Average Top Volume per Tree in each Plot, 1926 Block Plot M L K J I H G F E D A verage top volume per tree, i n cubic fe et 2 733 758 757 780 927 874 868 4 725 769 868 703 858 954 921 6 845 761 815 723 947 761 829 8 776 750 784 817 934 909 1014 10 755 777 800 869 1014 936 936 12 735 825 818 801 926 848 814 14 853 887 876 791 921 1115 881 783 16 812 831 888 804 855 992 596 710 18 787 827 825 803 921 917 860 895 20 699 821 935 893 945 1001 836 811 22 803 765 891 969 995 983 901 802 871 24 764 * 857 944 858 1005 898 761 799 26 759 799 778 819 857 979 829 889 28 862 823 863 840 863 965 973 839 30 756 754 847 887 854 930 866 877 32 799 791 799 904 845 797 918 1071 784 34 738 * 845 780 942 866 919 916 732 36 750 790 843 • 848 947 901 975 976 813 38 727 801 817 771 806 807 927 747 809 40 791 819 826 867 848 878 854 865 830 42 696 730 885 822 894 882 789 905 811 44 710 813 832 850 796 851 873 896 849 46 815 885 963 944 48 843 849 901 750 50 840 840 895 924 52 829 920 1006 847 54 855 959 * 823 * Plots omitted because of injury to trees. BlJL. 451] FERTILIZER TRIALS IN A BEARING CITRUS GROVE 21 The extent of the variation in top volume between the several plots is shown by table 3. This presents the average top volume per tree, in each plot, for the entire grove in 1926. The greatest range in variability is shown in comparing plot H-14 with E-16 ; the former, with an average top volume of 1,115 cubic feet, is 87 per cent larger than the latter plot, with only 596 cubic feet as an average top volume. The differences in top volume are somewhat larger than the 1 1 1 1 AA J.J.UU 1000 1 II 1 JJ L 1 1 L aoo p^^^^^^^^^^ftp^ 700 h| ?=JpE|EB|^gEHE5ti=|p ?|==Z?===I^H===E s *^2-&*5tt^^ ]--.- ===-S----j^s4C :-llsSrlEppSi|«feH^ g 100 SSi^^ feffl^:..:-: :-■ ^ ^52"^ "i I^^j^j^^ ^ ""'^npf -- " '-- -|"I4^" hr i~M~ "^ — ^n-f-^- ■ -;- -pt-' 4 !- — =t-=t=— y= 1 , 1 ! 1 — \— jh — _l ,_l JJ_ J — u — i 4_a_ _ j +-H-+ g 300 E^ihi+^l^^ o = -^-- r ^ K ^g ==fc _S i= -y^-^--^ = r--m-± jj|j = = = = - - - -- i | j 1 ■ j •~~~p~~ : T" - { |— z£ - - M T — - 3= = - ~ -j- ~~ z==— :4^— -d===te=i^-±=+z^H^ 1 — | — 1 l__l — i — ' — t — | 1—, 1-| 1 — LU — "°° RlMjllMT['l 4 Htn1-^ =t3= FT M ! 1 1 ' l "lTfflTtTffFl4nffllrn"l Mm =iiii=i=iiii=Eii|i=i=Ei^ _ E£_ ----- J= q= ~i ~ ' II 1 i ioo : l c-.c; ±±ci-^ i c±t±:_i l c l ~—i± tOCOOCM^vOCO O N reviously noted, because of pockot-gopher injury to the trees. BUL. 451] FERTILIZER TRIALS IN A BEARING CITRUS GROVE 35 TABLE 11 The Average Annual Yields Per Tree of the Ultimate Unit Plots of Forty- two Theoretical Treatments and the Average of Groups of Four such Plots Arranged on the Basis of Yield and other Factors Yield in pounds Treat- ment No. Yield in pounds Treat- ment No. Of ultimate unit plots Average for treat- ment Of ultimate unit plots Average for treat- ment 1 148 126 124 105 126 22 139 130 120 116 126 2 139 129 124 111 126 23 146 138 115 103 126 3 135 133 116 116 125 24 144 133 115 112 126 4 155 130 119 100 126 25 155 122 117 108 126 5 153 135 122 93 126 26 153 128 115 103 125 6 138 133 129 104 126 27 137 126 122 120 126 7 139 128 119 116 126 28 137 132 122 110 125 8 140 126 119 116 125 29 165 146 113 79 126 9 144 133 115 110 126 30 152 136 114 96 125 10 150 128 121 100 125 31 150 129 119 105 126 11 142 137 127 100 127 32 136 135 121 112 126 12 150 121 119 113 126 33 135 128 127 114 126 13 142 141 122 97 126 34 147 136 114 106 126 14 139 134 119 108 125 35 138 135 128 98 125 15 148 146 120 93 127 36 140 135 125 104 126 16 157 132 131 87 127 37 142 128 126 108 126 17 155 132 121 98 127 38 147 129 119 103 125 18 140 131 129 102 126 39 141 132 119 107 125 19 152 138 116 98 126 40 140 138 127 99 126 20 134 131 124 110 125 41 150 130 126 99 126 21 142 140 114 109 126 42 140 136 118 113 127 By this method the grouping of the plots to be used for individual fertilizer treatments has been accomplished in such a way that their average yields per tree prior to the start of the experiments are approximately the same, and within a very narrow range are equal to the average production per tree of the entire field. The table indicates that the average yearly production per tree for the highest-yielding group of plots is 127 pounds, while the average for the lowest- producing group is 125 pounds. By this arrangement 8 the best- yielding group has produced 1.6 per cent more fruit than the lowest yielding. This difference is practically negligible in trials of this sort. This arrangement was adopted in order that the greatest accuracy of comparison might be attained by the customary statistical methods. s In choosing the plots from each class to be used for a given treatment a particular effort was made, at the same time, to so locate them that the various repetitions of each treatment would be scattered satisfactorily from the point of view of variations in soil type, visual comparisons of .contrasting treatments, ease of culture, and adequate geographical distribution. P'ot A/t//n/>eAS Z 4 6 8 /O tZ M /€ /S ZO Z2 24 Z6 Z8 30 Si 34 36 38 40 41 44 4* 48 SO St S+ 40 35 41 20 3( 42 30 37 34 it a 24 26 11 IS 33 J n n 29 26 3038 23 34 40 ZO 38 32 29 13 35 25 18 37 27 42 14 31 24 16 36 33 27 11 17 33 32 38 23 35 25 28 36 13 39 36 26 30 22 \\ 13 27 a) 33 33 32 5 42 40 C 34 23 36 3G 37 32 28 22 20 10 40 23 16 26 30 23 41 35 37 39 17 25 13 14 34 42 33 2 4 6 8 10 /2 14 /6 /a ZO ZZ 14 26 ZB JO 3Z 34 36 38 40 4Z 44 P/o t AV/?7 ber*s Fitf. l.'i.— Diagram of experimental field showing location of the respective treatments by number. Bui*. 451] fertilizer trials in a bearing citrus grove 37 In case differences in relative production of various plots which have been observed to date do not prove to be maintained in the future, it may still be feasible to draw conclusions as to the effect of the treat- ments by taking into account the trend of changes in relative pro- ductivity in various sections of the field as indicated by the 25 'con- tinuity' plots, and by the use of standardized methods of measuring the significance of differences between groups of plots. The location in the field of each treatment is shown in figure 13. In this illustration the various plots are designated, first, by the letter of the block in which they occur, and, second by the number of the plot in the particular block. The letters designating the blocks are shown on the left margin, and plot numbers in each block are shown along the top and bottom margins of the diagram. The treat- ments assigned to each plot are indicated by numerals placed in each respective plot space. The treatment which each plot receives may be found by reference to table 12, which also contains a list of all plots receiving a given treatment. TABLE 12 List and Location of Treatments with Amounts of Certain Fertilizer Ingredients Applied During the Early Years of the Experiment (Four plots per treatment unless otherwise stated) Materials and treatment Pounds of nitrogen (N), phosphoric acid (P2O.,), potash (K2O), applied per tree per year from each material Location in field "C" (25 plots) Ammonium nitrate 0.33 N 0.17N 0.50 N D 8 F36 H48 K20 Blood D24 P'52 I 4 K44 Manure D38 G24 I 28 L10 D48 G44 J 8 L30 1. No treatment E 4 H16 .734 M 4 E20 H36 K 6 M24 M40 D18 G38 J38 L14 2. Ammonium nitrate No cover crop ION D22 F38 J40 M 6 3. Ammonium nitrate Triple superphosphate ION 1 P 2 Ot D28 G40 K40 L16 4. Ammonium nitrate Triple superphosphate ION 10 p 2 o 5 1.0 KsO D26 G42 K38 M16 No cover crop 5. Ammonium nitrate ION 1 K2O E22 F42 K32 M14 Sulphate of potash No cover crop 6. Cover crop alone (6 plots) ION D12 H32 J 4 L22 7. Ammonium nitrate E 6 H34 J12 1-28 Cover crop 38 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION Table 12 — (Continued) Materials and treatment 8. Ammonium nitrate Triple superphosphate Cover crop 9. Ammonium nitrate Triple superphosphate Sulphate of potash Cover crop 10. Ammonium nitrate Triple superphosphate Muriate of potash Cover crop 11. Ammonium nitrate Sulphate of potash Cover crop 12. Ammonium sulfate Nitrate of soda Blood Cover crop 13. Ammonium sulfate Nitrate of soda Blood Phosphate Sulphate of potash Cover crop 14. Ammonium nitrate Blood Manure Phosphate Muriate of potash Cover crop 15. Ammonium sulfate Cover crop 16. Ammonium sulfate Limestone Cover crop 17. Blood Cover crop 18. Urea Cover crop 19. Ammonium nitrate Blood Cover crop 20. Nitrate of lime No cover crop 21. Nitrate of lime in February Cover crop 22. Nitrate of lime in June Cover crop 23. Nitrate of lime in October Cover crop 24. Nitrate of lime in three applications Cover crop 25. Nitrate of lime Nitrate of soda Cover crop 26. Nitrate of soda No cover crop Pounds of nitrogen (N) , phosphoric acid (P2OO, potash (K2O) , applied per tree per year from each material 1.0N I.OP2O5 ION I.OP2O5 1.0 K2O ION I.OP2O5 1.0 K2O ION 1.0 K2O 0.33 N 0.33 N 0.33 N 0.33 N 0.33 N 0.33 N 1.25 P2O5 0.66 K2O 0.33 N 0.17N 0.50 N IOP2O5 1.0 K2O ION ION 1.0N ION 0.67N 0.33 N ION ION ION ION ION 50 N 0.50 N ION Location in field E12 H46 J18 L20 E14 I 42 J10 L18 E 2 H40 J14 L26 E16 H42 J22 L32 D 2 G48 I 12 M28 D 6 G50 I 10 M26 E 8 H50 J16 M30 D46 I 18 K30 M18 H20 J28 K42 M 2 F46 I 34 K22 M22 F50 I 6 K28 M12 F32 I 22 K10 M20 E18 F40 J32 L 6 D32 H24 I 40 LI 2 F48 H22 J30 M38 D42 H26 J42 L 2 D44 G32 I 24 K18 D54 G46 I 26 K12 D50 H30 J 2 L42 Eul. 451 FERTILIZER TRIALS IN A BEARING CITRUS GROVE 39 Table 12— (Concluded) Materials and treatment 27. 28. 30. 31 32. 33. Nitrate of soda Cover crop Nitrate of soda Gypsum Cover crop 29. Nitrate of soda Manure Cover crop Manure broadcast in fall No cover crop Manure broadcast in fall Cover crop Manure broadcast in spring Cover crop Manure in furrows in fall Cover crop 34. Ammonium nitrate Blood Manure Gypsum Cover crop 35. Ammonium nitrate Blood Manure Limestone Cover crop Alfalfa hay on nitrogen basis Ammonium nitrate Blood Cover crop Bean straw on nitrogen basis Ammonium nitrate Blood Cover crop Wheat straw on nitrogen basis Ammonium nitrate Blood Cover crop 39. Wheat straw on organic matter basis Ammonium nitrate Blood Cover crop 40. Amount halved Ammonium nitrate Blood Manure Cover crop Amount doubled Ammonium nitrate Blood Manure Cover crop Amount trebled Ammonium nitrate Blood Manure Cover crop 36 37 38. 41 42. Pounds of nitrogen (N), phosphoric acid (P2O5), potash (K2O), applied per tree per year from each material ION ION 50 N 0.50 N ION 1.0N ION ION 0.33 N 0.17N 0.50 N 0.33 N 0.17N 0.50 N 50 N 0.33 N 0.17N 0.50 N 0.33 N 0.17N 0.50 N 0.33 N 0.17N 0.13*N 0.58 N 0.29 N 17N 0.08 N 0.25 N 0.67N 33 N ION 1.00 N 50 N 1 50 N Location in field D52 G22 I 32 D40 H18 J26 F44 I 2 K36 D30 I 30 K 2 D20 I 36 K16 G34 I 38 K24 F34 H54 J20 D36 H52 J36 D10 H28 J44 G30 I 20 K26 D34 H38 I 14 G26 K 4 G28 H14 J24 D 4 G36 J 6 E10 G52 I 44 E24 G54 I 16 K14 L38 M 8 M42 M34 L 8 M32 L 4 M10 M36 L44 L36 M44 L40 K 8 K34 * Based on analysis of material applied spring of 1927. 40 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION DIFFERENTIAL FERTILIZER AND CULTURAL TREATMENTS The gradual increase in the knowledge of the culture and nutri- tion of citrus fruits has raised a large number of questions for solu- tion which may properly be included among the trials under con- sideration. However, the purposes of these trials are not confined to the determination of the effect of specific treatments on the produc- tion of oranges alone. It is expected that the effect of many of the fertilizer treatments may cause such ultimate differences in the soil conditions, that valuable material will be produced for future labora- tory studies upon the fundamental processes which may be involved. The effect of some of the treatments may not be apparent during the early progress of the trials, but the continued application of these materials may have a gradual effect upon both the trees and the soil 9 which may be cumulative with the passing of time. The great diversity and the seeming importance of the problems which have been raised have prompted an effort to secure suggestions from many sources. On August 28, 1926, a general meeting was called for this purpose at the Citrus Experiment Station by the Director. Citrus growers, members of the Staff of the College of Agriculture and those interested in the sale of fertilizer materials, have all contributed to the plans finally adopted. Frequent con- ferences have been held informally with these persons. 9 In order that adequate material may be supplied for laboratory studies upon the source of changes which may be produced in the soil after various treatments, the soil of this orchard has been thoroughly sampled, once during the winter of 1918-19, and again at the time the differential treatments com- menced in February, 1927. These samples are now in storage. It is planned that soil samples will be taken at periodic intervals throughout the duration of the experiments for use in laboratory studies. Although the materials which will be applied will be as pure as it is practicable to purchase commercially, it is also planned that samples of them will be taken for future study. Hence, it may be possible to determine whether or not the effects of the treatment are actually due to the material being consciously tested, or to the effects of impurities in it. The arrangement of the experimental field and the nature of the trials which are described are the results of the combined efforts of a large number of people. In connection with the planning of the treatments suggestions have been sought from many sources. The advice of many mem- bers of the staff of the Citrus Experiment Station lias been of great influence in determining the nature of the trials to be made. Among these men are H. J. Webber, A. R. C. Haas, W. P. Kelley, W. R. Schoonover, J. Gordon Surr, and R. S. Vaile. The successful supervision of the field work, which is essen- tial to an experiment of this kind, has been due at various times to the efforts of W. M. Mertz, J. A. Prizer, and Charles Wilson. BuL. 451] FERTILIZER TRIALS IN A BEARING CITRUS GROVE 41 The trials indicated in table 12 have been selected as incorporating the most essential ideas involved in the suggestions which have been made. The elimination of many trials which possibly would have contributed much valuable information was necessitated by the physical limitations of the experimental field. As heretofore stated, each of the 42 treatments is repeated four times. These repetitions are distributed on the basis which has been discussed in the previous section of this paper. The location of each in the field is shown in table 12. In general the amounts of the ele- ments or materials applied are in harmony with conservative com- mercial practice. During the early years of the trials it is expected that, unless otherwise stated, one pound of actual nitrogen (N), phosphoric acid (P 2 5 ), and potash (K 2 0), respectively, will be applied per tree each year, in each instance where these materials are used. This general rule is to be followed regardless of the material by which they are supplied. Gypsum and limestone are to be used at the rate of one ton per acre per year, the gypsum to be supplied annually and the limestone every four years. The concentrated fer- tilizers are to be applied in the early spring unless otherwise stated. The bulky organic materials are to be applied in the late summer or early fall with the exception of one treatment. Any discussion or grouping of the treatments on the basis of their experimental purposes involves some duplication and perhaps some confusion. Many comparisons may be made between a single trial and several other trials, not all of which can be placed in a simple out- line of comparison. In indicating the general scope and some of the chief divisions of the experiments, however, it may be well to call attention to the treatments which most obviously fall under each division. The more general groups of treatments to be employed follow. Experimental trials are referred to by number, the exact treatment of which may be obtained from table 12. A. As heretofore noted, 25 plots, designated as 'C plots, have been distributed throughout the field to indicate the degree of the continuity of differences of normal yield of various parts of the field. These plots will serve as indices of relative fertility and will be an aid in the interpretation of all results. The standard amount of one pound of nitrogen per tree is to be applied annually during the first few years of the experiment. One-half the nitrogen is to be in the form of concentrated materials applied in the spring, and one-half as bulky organic material applied in the fall. The concentrated mate- 42 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION rials will consist of ammonium nitrate, which will supply % pound of nitrogen, and dried blood, which will supply % pound of nitrogen. The bulky organic material will be dairy manure, and will supply one-half the total nitrogen applied. Winter cover crops will also be grown on all C plots. B. A series of trials have been installed to determine the effects of nitrogen, phosphoric acid, and potash, with and without a cover crop. This group of treatments may be subdivided as follows: I. Ten treatments involve essentially the use of ammonium nitrate (N), triple superphosphate (P), sulphate of potash (K), and cover crop. The materials are applied in standard quantities alone and in the following combinations: Clean culture Cover crop No. No. 6. 7. 2. N N 3. N P — 8. N P — 4. N P K 9. N P K 5. N — K 11. N — K II. One treatment (No. 10) substitutes muriate of potash in treat- ment 9 above to determine the possible effect of accumulations of chlorin as compared with the sulfate radicle in the presence of nitrogen and phosphoric acid. III. Two trials (Nos. 12 and 13) were inaugurated to determine the value of phosphoric acid and potash in the presence of several nitrogen-carrying fertilizers combined. The standard amount of actual nitrogen, one pound per tree, has been used, but the approxi- mate proportions of the materials used to supply it, and also the amounts of phosphoric acid and potash used, have been determined by averaging the four most popular so-called 'complete commercial fertilizers' used at the present in citrus orchards. This average gave fertilizers of the order of 7.5 per cent N, 9.25 per cent P 2 5 , 4.75 per cent K 2 0. When all fillers are eliminated this becomes 9.7 :11.9 :6.15, which is the formula employed. The materials used are ammon- ium sulfate, nitrate of soda, and blood (each supplying one-third of the total nitrogen), triple-superphosphate and sulfate of potash. The 'complete fertilizer' has been commercially mixed. These two trials may logically be compared directly with several others in this series, as a study of table 12 will show. IV. One trial (No. 14) deals with the value of additions of phos- phoric acid and potash in the presence of manure when the latter is BUL. 451] FERTILIZER TRIALS IN A BEARING CITRUS GROVE 4.'} supplied in such an amount that it provides one-half the total quantity of nitrogen applied. V. The necessity of nitrogenous fertilization in the culture of citrus fruits in California has stimulated the adoption of an extensive series of trials of nitrogen-carrying materials (Nos. 2, 7, 15, 16, 17, 18, 19, 20, 21, 26, 27, 28, 29, 30, 31). These have been chosen in an effort to determine the efficiency of various substances supplying equal amounts of total nitrogen. The results of continued applications of various chemical constituents associated with the carriers, and the interrelations of several of these constituents will also be the subject of study. The effect of the so-called 'soil amendments' may also be considered in this section, since they contain chemical constituents which may react with the fertilizer material. Clean culture and cover cropping will be employed in special instances in an attempt to deter- mine the effect of organic matter on the soil reactions to various fertilizer materials as well as on tree growth. VI. The effect of supplying nitrogenous material at various seasons will be studied (Nos. 21, 22, 23, 24, 31, 32). These materials will consist of nitrate of lime and dairy manure, respectively, each to supply the standard amount of nitrogen. The nitrate of lime will provide nitrogen in an available form and will give some information as to the time at which citrus trees require this material for best response. The manure will serve for the study of the reaction of the tree and soil to organic and slowly available nitrogenous materials when applied at different seasons. VII. The method of applying bulky organic materials (Nos. 31, 32, 33) is the subject of a trial comparing the application of dairy manure by means of broadcasting and in furrows. VIII. Four trials (Nos. 16, 28, 34, and 35), are being made to determine the effects of soil amendments under various conditions of culture. IX. The effect of the addition of various bulky organic materials is to be studied in an effort to determine the specific effect of such materials, the desirable amount of organic matter to apply, and also the value of materials low in nitrogen. In certain trials the organic materials will be applied in such a quantity that they will supply half the total nitrogen (Nos. 36, 37, 38, and C). The amount of organic matter will therefore vary in quantity with the materials used. In another trial (No. 39) the bulky materials will be applied in such amounts that the organic matter to be added in the form of 44 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION wheat straw will be equal to that contained in dairy manure when the latter material supplies half the total nitrogen. In all cases the total nitrogen applied will be made up to the standard amounts with ammonium nitrate and dried blood. X. The effect upon trees and soil of supplying various total amounts of nitrogen will be investigated in certain trials (Nos. 40, 41, 42, and C). These experiments will serve as a guide in determining the standard amount of this element to be applied in the future years on this experimental field. They may also give some information as to the most economical use of nitrogenous fertilizers on Ramona loam and on similar soil types. The nitrogen in this series of trials is to be derived from concentrated and bulky material as follows : two-sixths of the total amount to be supplied by ammonium nitrate, one-sixth by dried blood, and three-sixths by dairy manure. APPENDIX COST OF DEVELOPING AND MAINTAINING THE EXPEEIMENTAL GEOVE DUEING THE FIEST TEN-YEAE PEEIOD A record has been kept of the expenses incurred in the develop- ment of the experimental orchard. Several of the ordinary items of expense which must be met by the commercial grower have naturally not been among the necessary charges met by a state institution. Among such charges are taxes, interest on investment and, in this particular instance, the usual expense of water rights, which may normally be charged against such an enterprise. The actual cost of the development as experienced can not, therefore, be used as an absolute criterion of the expense which may be anticipated in connec- tion with the establishment of a commercial orchard. It may, how- ever, be interesting to present the record of the actual cost of develop- ment plus the ordinary average charges which would have been made against such a property were it owned and financed by a private commercial organization. The actual ten-year expenditure for development by the Experi- ment Station, including original capital investment less the assumed charge of $200 an acre for water, plus material and labor equals $1,508.26 an acre. During the same period the sale of the bean inter- crops plus the sale of the fruit totaled $1,653.13. The orchard has thus repaid all capital expenditure and costs of operation, and shows a balance of $144.87 an acre to the Experiment Station at the end of the first ten-year period. Bul. 451 FERTILIZER TRIALS IN A BEARING CITRUS GROVE 45 TABLE 13 Summary of Accumulated Cost Per Acre of Developing Orange and Grapefruit Orchard (Includes charges for supervision, taxes, depreciation and interest. Sales are credited.) Material and labor Supervi- sion and miscel- laneous labor Taxes* Inter- est*! at 6% Total charges Sales total net returns Net debit Net credit Total accumu- lated invest- ment Original capital investment $676,101: $ 676.10 July I, 1917, to June 30, 1918.. 45.63 $37.46 $ 5.00 $40.57 $128.66 $ 46 19$ $ 82.47 758.57 July 1, 1918, to June 30, 1919... 51 75 37.46 5.00 45 51 139.72 25.16§ 114.56 873.13 July 1, 1919, to June 30, 1920. . 69.23 37.46 5 00 52.39 164.08 54 08§ 110.00 983.13 July 1, 1920, to Dec. 31, 1920. 22.54 18.73 2.50 29.49 73.26 46.23§ 27.03 1010 16 Jan. 1, 1921, to Dec. 31, 1921.. 99.30H 37.46 ! 7.00 60.61 204.37 56.481 147.89 1158 05 Jan. 1, 1922, to Dec. 31, 1922... 86.79 37 46j 7.00 69.48 200.73 184.771 15.96 1174 01 Jan. 1, 1923, to Dec. 31, 1923... 291.60+ 37.46 11.00 70 44 410.50 55.571 354.93 1528 94 Jan. 1, 1924, to Dec. 31, 1924. 156.4411 37 46 11.00 91.74 296. 64* 215.151 81.49 1610 43 Jan. 1, 1925, to Dec. 31, 1925... 94.72 37 46 11 00 96.63 239. 81 x 495.911 $256 10 1354 33 Jan. 1, 1926, to Dec. 31,1926. 114.1611 37.46 11.00 81.26 . 243. 88 x 473.591 229.71 1124.62 * Charges made but not actually paid. t Interest is charged on total accumulated investment existing at end of previous fiscal period, but not on operating charges or surplus of the current period. % Includes charges as follows Cost of land $300.00 Average cost of water 200.00 Pipe lines, installed 91.40 Preparing land 10.00 Digging holes 2.70 Balling trees 4 50 Trees, 90 at 75 cents 67.50 Total $676.10 § Receipts from sale of beans. || Includes charges for fumigation. 1 Receipts from sale of fruit. + Includes $202.64 for orchard heating equipment x Includes depreciation on heating equipment at 5 per cent per annum ($10.13). 46 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION The figures presented in table 13, on the other hand, show the normal costs of developing the grove if such charges as taxes, water rights, and interest on capital invested were charged against the undertaking. The figures given herein may, therefore, be used by the reader as a basis of comparison and as an aid in estimating the cost of establishing a commercial grove. It will also be our endeavor to show where the charges made and the receipts obtained may be in any way uncommon, in order that the records may not be mislead- ing if taken as a reasonable estimate of such costs. The actual capital investment per acre for land, a theoretical charge for water rights, 10 the cost of installation of pipe lines, and that of planting of trees are indicated in a footnote to table 13. Although pipe lines are located at 200-foot intervals and the cost of this item is greater than in the usual planting, the costs of other items are rather low. The price of the land, $300, is low compared with the present ruling prices being paid in this and other comparable orange-growing districts. The cost of trees is somewhat below the average, the trees were all grown at the Experiment Station. The frost-protection equipment purchased in 1923 and charged in table 13, consists partly of fifty 9-gallon heaters per acre, one 500- gallon tank wagon to each 8 acres, sufficient oil storage and oil to refill all of the heaters four times, a frost-alarm system, filling buckets, and torches. The initial charge for this equipment was $202.64 per acre. Depreciation has been charged on this equipment at the rate of 5 per cent per annum. No other investment charge for equipment has been made for this particular grove. The tools, teams, and tractor used on all projects of the Experiment Station have been employed, and flat charges have been made against this acreage according to the services rendered. The cultivation work has been done mainly with a tractor. The prevailing rate of $2.50 an hour has been charged for all tractor work. The rate charged for team work has been $0.75 an hour for team and man. Other labor has been charged at current rates. The charge for irrigation water has approximated very closely the average which would have been experienced had actual stock in the Gage Canal Company been held by this property. This average is $10.65 an acre annually for the average amount used. Nearly all the !<> A theoretical charge of $200 per acre for water rights is included. The grove is in the midst of a large acreage of citrus served by the Gage Canal Co. The average market value per acre of stock of this system commonly used is therefore used as the theoretical charge. (See Blaney, Harry F. Cost of water to irrigators in California. California State Dept. Public Works, Div. Eng. and Irrig. Bui. 8:1-66. 1925.) BUD. 451] FERTILIZER TRIALS IN A BEARING CITRUS GROVE 47 fertilizer which has been used has been the legumes grown on the land, excepting that one-half ton of alfalfa straw per acre was pur- chased in 1924, and spread in the irrigation furrows to retard the movement of irrigation water and facilitate its penetration. Certain cultural costs are higher than would occur in commercial practice. Extra care has been taken to have all of the operations done as uni- formly and exactly as possible over the entire planting. This is particularly true of irrigation. Certain charges included under super- vision are for record keeping. These charges are for weighing of beans and of fruit, measuring the top volume and trunk circumference of the trees, etc. This property has been favored with comparative freedom from serious tree diseases. Insect pests have been readily kept under con- trol. Fumigation has been necessary only three times, in 1921, 1924, and 1926. The grove has returned some revenue every year since and includ- ing the year it was planted. The returns the first four years were from the sale of Black-eye beans, grown on the land as an intercrop. The total receipts for the four years from the sale of beans were $171.66 an acre. This very favorable return was influenced by the fact that the beans were grown during and immediately following the period of the World War when especially high prices were received for this commodity. In spite of the return from the sale of beans during the first four years, the cultural maintenance charges were such that the capital investment had increased to $1,010.16 an acre at the time when the trees came into production. The total amount received from the sale of fruit for all years was $1,481.47 an acre, and represents the value of six crops of fruit from the grove, from its fourth year to and including its ninth year. All of the fruit has been sold by the California Fruit Growers Exchange. The returns over the six-year period include the usual fluctuations in prices. Table 13 indicates the capital investment under the heading " Total accumulated investment" at the close of each fiscal year from the time of planting until June 30, 1920, and for each calendar year from that time until December 31, 1926. It may be observed that the first year in which an actual profit occurred was 1925, at which time the orchard was eight years old. The capital investment was decreased both that and the following year. At the close of the period under discussion the total investment amounted to $1,124.62, which is the net cost of the grove per acre to December 31, 1926. An evaluation of the grove with its improvements by a disinterested professional 48 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION appraiser was made at that time. A conservative estimate of $1,500 per acre was arrived at. It was stated that this amount should be realized if the property were disposed of at a forced sale. The differ- ence between this figure and the total accumulated cost represents the theoretical profit from the undertaking from a commercial point of view. This figure amounts to $375.38 per acre, or $18,037.01 for the entire tract of 48.05 acres. TABLE 14 Net Beturns* for Varieties per Pound, 1921-1926, Inclusive Variety or kind 1921 1922 1923 1924 1925 1926 Average Navels Valencias Grapefruit $0.02125 .02162 .01981 $0.04810 .03349 .04261 $0.02125 .01311 — .00649 t $0.01092 .02403 .01653 $0.04212 .05962 .03498 $0 03228 .03423 .03166 $0.02932 .03107 .02318 * Net to grower. t Packing, selling, and transportation charges exceeded the gross returns by this amount. The net prices received per pound for each variety of citrus — Valencia and Navel oranges and Marsh Seedless grapefruit — each year, are noted in table 14. In general they are typical of average prices paid during these years, and are influenced by the usual factors affecting supply and demand. The value per pound of all marketable fruit was increased in 1922 by the occurrence of a freeze which cut down the total amount of fruit shipped. This freeze did not, however, affect the accuracy of the yield records of Navel oranges. Heaters were installed in 1923, and no further loss has been experienced from this source. Although the average price has been satisfactory, the returns per pound from the sale of grapefruit have been more variable than from the sale of the two varieties of oranges. As a basis of comparison of the returns from the three varieties of fruit, their production has been calculated as if they were in a solid planting. The average yield of a solid acre of each variety is noted in table 15 for each of the six years under discussion, as well as the total for this period. The heavier production of grapefruit is notable. The total production of Navels and Valencias is about equal, but it is apparent that certain years have been more favorable for the production of one variety than for the other in this particular orchard under conditions of uniform care. In 1922, for example, the damage from frost was not so severe in the cases of the Valencias and the grapefruit as in the case of the Navels. The yield of Navels was markedly higher than that of Valencias in 1925 for some reason which has not been ascertained. BUL. 451] FERTILIZER TRIALS IN A BEARING CITRUS GROVE 49 The total gross return from all three varieties has been calculated on the acre basis and appears in table 16. Over the six-year period Valencias and grapefruit have netted about an equal amount and have been slightly more profitable than Navels. The greater return from grapefruit during 1921 and 1922 is a noticeable feature of this table, although an actual loss occurred with this crop in 1923. TABLE 15 Yield of Varieties on an Acre Basis, (Pounds) 1921-1926, Inclusive Variety or kind 1921 1922 1923 1924 1925 1926 Total Navels Valencias Grapefruit l,945f 1,948 4,535 2,669* 5,330 6,125 6,168f 5,855 9,160 ll,924f 10,649 16,881 13, 085 f 8,227 12,377 10,678f 15,999 17,606 46,469 48.008 66,684 * Based on an area of 18.29 acres of Navels, 14.99 acres of Valencias, and 14.77 acres of grapefruit; total area, 48.05 acres. t Navel yields in this table are somewhat lower than those in table 6, the latter includes windfalls, whereas this table records only fruit which went to packing house. | This is only 37 per cent of total production, remainder not sold on account of frost injury. TABLE 16 Gross Returns* for each Variety per Solid Acre, 1921-1926, Inclusive Variety or kind 1921 1922 1923 1924 1925 1926 Total Navels Valencias Grapefruit $41.33 42.11 89.82 $128.37 178.50 260.98 $131 07 76.76 —59.45 $130.21 255.90 279.04 $551 14 490.49 432.95 $344.69 547 54 557.40 41,326.81 1.591 30 1,560.74 Charges for picking and hauling have been deducted The reader should not use tables 13, 15, and 16 as an indication of the returns which may be reasonably expected from a commercial grove without being fully aware that the average prices set forth in table 14 from 1921 to 1926, inclusive, are considerably above the ten- year average of 1912-22. Furthermore the average price received from the sale of oranges for the years 1925 and 1926, 3.7 cents a pound for Navels and 4.7 cents a pound for Valencias, is approximately double the average return for the ten-year period 1912-22. 1X It was during these two years of high prices that two out of the three really commercial yields were obtained from this orchard. The total returns have, therefore, been considerably higher than can be expected on the average from similar orchards. 11 Vaile, K. S. A survey of orchard practices in the citrus industry of southern California. California Agr. Exp. Sta. Bui. 374:1-40. 1924. STATION PUBLICATIONS AVAILABLE FOE FREE DISTRIBUTION BULLETINS No. No. 253. Irrigation and Soil Conditions in the 386. Sierra Nevada Foothills, California. 262. Citrus Diseases of Florida and Cuba 387. Compared with those of California. 388. 263. Size Grades for Ripe Olives. 268. Growing and Grafting Olive Seedlings 389. 273. Preliminary Report on Kearney Vine- 390. yard Experimental Drain, Fresno County, Calif. 391. 277. Sudan Grass. 278. Grain Sorghums. 392. 279. Irrigation of Rice in California. 393. 283. The Olive Insects of California. 394. 304. A Study of the Effects of Freezes on Citrus in California. 310. Plum Pollination. 395. 313. Pruning Young Deciduous Fruit Trees. 396. 324. Storage of Perishable Fruits at Freez- ing Temperatures. 397. 328. Prune Growing in California. 331. Phylloxera-resistant Stocks. 398. 335. Cocoanut Meal as a Feed for Dairy 400. Cows and Other Livestock. 402. 340. Control of the Pocket Gopher in 404. California. 405. 343. Cheese Pests and Their Control. 406. 344. Cold Storage as an Aid to the Mar- 407. keting of Plums, a Progress Report. 347. The Control of Red Spiders in Decid- uous Orchards. 408. 348. Pruning Young Olive Trees. 409. 349. A Study of Sidedraft and Tractor Hitches. 350. Agriculture in Cut-Over Redwood Lands. 410. 353. Bovine Infectious Abortion, and As- sociated Diseases of Cattle and New- born Calves. 411. 354. Results of Rice Experiments in 1922. 357. A Self-Mixing Dusting Machine for 412. Applying Dry Insecticides and Fun- gicides. 358. Black Measles, Water Berries, and 414. Related Vine Troubles. 361. Preliminary Yield Tables for Second- 415. Growth Redwood. 416. 362. Dust and the Tractor Engine. 363. The Pruning of Citrus Trees in Cali- 417. fovnia. 364. Fungicidal Dusts for the Control of 418. Bunt. 366. Turkish Tobacco Culture, Curing, 419. and Marketing. 367. Methods of Harvesting and Irrigation 420. in Relation to Moldy Walnuts. 368. Bacterial Decomposition of Olives 421. During Pickling. 422. 369. Comparison of Woods for Butter Boxes. 423. 370. Factors Influencing the Development of Internal Browning of the Yellow 424. Newton Apple. 371. The Relative Cost of Yarding Small 425. and Large Timber. 426. 373. Pear Pollination. 374. A Survey of Orchard Practices in 427. the Citrus Industry of Southern California. 428. 375. Results of Rice Experiments at Cor- tena, 1923, and Progress in Experi- ments in Water Grass Control at the 429. Biggs Rice Field Station, 1922-23. 430. 377. The Cold Storage of Pears. 431. 379. Walnut Culture in California. 380. Growth of Eucalyptus in California 432. Plantations. 382. Pumping for Draininge in the San 433. Joaquin Valley, California. 385. Pollination of the Sweet Cherry. Pruning Bearing Deciduous Fruit Trees. Fig Smut. The Principles and Practice of Sun- Drying Fruit. Berseem or Egyptian Clover. Harvesting and Packing Grapes in California. Machines for Coating Seed Wheat with Copper Carbonate Dust. Fruit Juice Concentrates. Crop Sequences at Davis. I. Cereal Hay Production in Cali- fornia. II. Feeding Trials with Cereal Hays. Bark Diseases of Citrus Trees in Cali- fornia. The Mat Bean, Phaseolus Aconitifo- lius. Manuf acture of Roquefort Type Cheese from Goat's Milk. Orchard Heating in California. The Utilization of Surplus Plums. The Codling Moth in Walnuts. The Dehydration of Prunes. Citrus Culture in Central California. Stationary Spray Plants in California. Yield, Stand, and Volume Tables for White Fir in the California Pine Region. Alternaria Rot of Lemons. The Digestibility of Certain Fruit By- products as Determined for Rumi- nants. Part I. Dried Orange Pulp and Raisin Pulp. Factors Influencing the Quality of Fresh Asparagus after it is Har- vested. Paradichlorobenzene as a Soil Fumi- gant. A Study of the Relative Value of Cer- tain Root Crops and Salmon Oil as Sources of Vitamin A for Poultry. Planting and Thinning Distances for Deciduous Fruit Trees. The Tractor on California Farms. Culture of the Oriental Persimmon in California. Poultry Feeding : Principles and Prac- tice. A Study of Various Rations for Fin- ishing Range Calves as Baby Beeves. Economic Aspects of the Cantaloupe Industry. Rice and Rice By-Products as Feeds for Fattening Swine. Beef Cattle Feeding Trials, 1921-24. Cost of Producing Almonds in Cali- fornia : a Progress Report. Apricots (Series on California Crops and Prices). The Relation of Rate of Maturity to Egg Production. Apple Growing in California. Apple Pollination Studies in Cali- fornia. The Value of Orange Pulp for Milk Production. The Relation of Maturity of Cali- fornia Plums to Shipping and Dessert Quality. Economic Status of the Grape Industry. Range Grasses of California. Raisin By-Products and Bean Screen- ings as Feeds for Fattening Lambs. Some Economic Problems Involved in the Pooling of Fruit. PoAver Requirements of Electrically Driven Manufacturing Equipment. bulletins- no. 434. Investigations on the Use of Fruits in Ice Cream and Ices. 435. The Problem of Securing Closer Relationship Between Agricultural Development and Irrigation Con- struction. 436. I. The Kadota Fig. II. Kadota Fig Products. 437. Economic Aspects of the Dairy In- dustry. 438. Grafting Affinities with Special Refer- ence to Plums. 439. The Digestibility of Certain Fruit By- products as Determined for Rumi- nants. Part II. Dried Pineapple Pulp, Dried Lemon Pulp, and Dried Olive Pulp. CIRCULARS No. No. 87. Alfalfa. 257. 115. Grafting Vinifera Vineyards. 117. The selection and Cost of a Small 258. Pumping Plant. 259. 127. House Fumigation. 261. 129. The control of Citrus Insects. 264. 136. Melilotus Indica as a Green-Manure Crop for California. 265. 144. Oidium or Powdery Mildew of the 266. Vine. 157. Control of Pear Scab. 267. 164. Small Fruit Culture in California. 166. The County Farm Bureau. 269. 173. The Construction of the Wood-Hoop 270. Silo. 273. 178. The Packing of Apples in California. 276. 179. Factors of Importance in Producing 277. Milk of Low Bacterial Count. 202. County Organization for Rural Fire 278. Control. 203. Peat as a Manure Substitute. 279. 209. The Function of the Farm Bureau. 212. Salvaging Rain-Damaged Prunes. 281. 215. Feeding Dairy Cows in California. 217. Methods for* Marketing Vegetables in California. 282. 230. Testing Milk, Cream, and Skim Milk for Butterfat. 283. 231. The Home Vineyard. 284. 232. Harvesting and Handling California 286. Cherries for Eastern Shipment. 287. 234. Winter Injury to Young Walnut 288. Trees During 1921-1922. 289. 238. The Apricot in California. 290. 239. Harvesting and Handling Apricots 292. and Plums for Eastern Shipment. 293. 240. Harvesting and Handling California 294. Pears for Eastern Shipment. 296. 241. Harvesting and Handling California Peaches for Eastern Shipment. 298. 243. Marmalade Juice and Jelly Juice from Citrus Fruits. 300. 244. Central Wire Bracing for Fruit Trees. 301. 245. Vine Pruning Systems. 302. 248. Some Common Errors in Vine Prun- 304. ing and Their Remedies. 305. 249. Replacing Missing Vines. 306. 250. Measurement of Irrigation Water on the Farm. 307. 252. Support for Vines. 308. 253. Vineyard Plans. 309. 254. The Use of Artificial Light to In- 310. crease Winter Egg Production. 255. Leguminous Plants as Organic Fer- 311. tilizers in California Agriculture. (Continued) No. 440. The Feeding Value of Raisins and Dairy By-Products for Growing and Fattening Swine. 441. The Electric Brooder. 442. Laboratory Tests of Orchard Heaters. 443. Standardization and Improvement of California Butter. 444. Series on California Crops and Prices : Beans. 445. Economic Aspects of the Apple In- dustry. The Small-Seeded Horse Bean (Vicia faba var. minor). Thinning Deciduous Fruits. Pear By-Products. Sewing Grain Sacks. Preliminary Essentials to Bovine Tu- berculosis Control in California. Plant Disease and Pest Control. Analyzing the Citrus Orchard by Means of Simple Tree Records. The Tendency of Tractors to Rise in Front; Causes and Remedies. An Orchard Brush Burner. A Farm Septic Tank. Saving the Gophered Citrus Tree. Home Canning. Head, Cane and Cordon Pruning of Vines. Olive Pickling in Mediterranean Countries. The Preparation and Refining of Olive Oil in Southern Europe. The Results of a Survey to Deter- mine the Cost of Producing Beef in California. Prevention of Insect Attack on Stored Grain. Fertilizing Citrus Trees in California. The Almond in California. Milk Houses for California Dairies. Potato Production in California. Phylloxera Resistant Vineyards. Oak Fungus in Orchard Trees. The Tangier Pea. Alkali Soils. The Basis of Grape Standardization. Propagation of Deciduous Fruits. Control of the California Ground Squirrel. Possibilities and Limitations of Coop- erative Marketing. Coccidiosis of Chickens. Buckeye Poisoning of the Honey Bee. The Sugar Beet in California. Drainage on the Farm. Liming the Soil. A General Purpose Soil Auger and Its Use on the Farm. American Foulbrood and Its Control. Cantaloupe Production in California. Fruit Tree and Orchard Judging. The Operation of the Bacteriological Laboratory for Dairy Plants. The Improvement of Quality in Figs. The publications listed above may be had by addressing College of Agriculture, University of California, Berkeley, California. 2lw L'28