UNIVERSITY OF CALIFORNIA COLLEGE OF AGRICULTURE AGRICULTURAL EXPERIMENT STATION BERKELEY, CALIFORNIA CROP SEQUENCES AT DAVIS JOHN W. GILMORE BULLETIN 393 October, 1925 UNIVERSITY OF CALIFORNIA PRINTING OFFICE BERKELEY, CALIFORNIA 1925 Digitized by the Internet Archive in 2012 with funding from University of California, Davis Libraries http://www.archive.org/details/cropsequencesatd393gilm CROP SEQUENCES AT DAVIS JOHN W. GILMORE* The purpose of this bulletin is to set forth the trends of the yields of some cereal crops under several rotation practices in relation to certain soil and climatic conditions and the use of green manures. The data cover the ten-year period from 1914 to 1923 inclusive ; and for convenience of interpretation the results of the first and second (jsiWEflsrry of i:auh»ma fORNSA I ■ tOUEGE OF Al.B!ClSLTt;*£ -Twt mm ■ '■"».; *\,.w » BCf ^ J. ' j&B-f Ik ? — ^L BI , ' -^ k w i4 Fig. 1. — Continuous production of the same crop depletes the yield. 1. Wheat, fallow, barley, peas.. ..average yield 42.3 bushels per acre 2. Wheat, alternate fallow average yield 40.0 bushels per acre 3. Wheat alternate vetch average yield 38.7 bushels per acre 4. Wheat continuously average yield 22.6 bushels per acre five-year periods, where possible, are shown in comparison. Obviously a ten-year period for data of this kind is not sufficient for definite conclusions to be drawn in all instances. As time goes on the data will become more comprehensive and have increased significance. It is believed, however, that the data herewith presented show clearly the general trends of certain practices under the conditions existing at Davis. Division of agronomy. UNIVERSITY OF CALIFORNIA EXPERIMENT STATION TABLE 1 Arrangement of Plots, Their Treatment and Yields Bu. Per Acre Plot No. Wheat continuously.. Wheat, cultivated- fallow Wheat, cloddy — fallow Check Wheat, weedy — fallow Barley continuously. Check Rye continuously Oats continuously Check Wheat— manure con- tinuously Milo continuously — Check Saccari ne— sorgh um continuously 1 Wheat, wheat, fallow Check Wheat, fallow, wheat Fallow, wheat, wheat Check Wheat, wheat, wheat, fallow Wheat, barley, fallow Check Oats, wheat, barley, fallow Barley, milo, wheat, fallow Check Milo, wheat, fallow, barley Wheat, fallow, bar- ley, milo Check Fallow, barley, milo, wheat Barley, peas, wheat, fallow Check.. Peas, wheat, fallow, barley Wheat, fallow, bar- ley, peas Check Fallow, barley, peas, wheat Wheat, peas 13-14 14.5 19.3 11.3 13.6 50.4 61.2 14.1 79. 4€ 16.3 7. 9.3 11.3 8.3 9.1 11.6 11.3 10.6 59.3 63.6 12.3 64.64 17.8 17.6 58 21.3 3.34' 22.3 26. 30 14-15 23.67 24.83 40.80 26. 21.5 51.56 22.33 23 86.62 20.83 12.6 17.33 20.33 18.17 14.83 13. 36.4 14.83 18. 78.21 8.50 13.50 11.17 37 40 5.36 7. 27.33 7.67 15-16 38.33 51.67 50.67 38.33 43.00 60.60 36 12.16 80 39.33 42.33 61.67 38.67 7.73 41. 60.67 48.33 44 54.67 52.67 51.67 tO 4 36.67 20 20 58.33 32.33 70.40 25.67 3.63 44 67 16-17 41.50 46.00 74.2 54 38.6 122.5 45.33 65.6 48.5 9.6 57.16 47.16 51.33 42 53.66 40.33 43.66 72.80 35 45.33 43.6 10.51 32.16 65 7.25 17-18 25.8 46.8 44.3 42 42.3 67.7 38.8 33.5 84.3 33.3 39.3 7.11' 37.5 5.62 39. 24.1 49.3 37. 42.3 71.2 35 1 79.6 62.5 38.8 7 32.6 70.8 25.3 13.7 = 49.3 25.5 52.3 18-19 28.7 27.5 27.4 22 14 27.3 32.2 21.3 26.6 27.8 3.12 17.4 17.4 19.6 12.5 13.7 13.7 2.75 12.1 24.5 13 5 44 2 3.75 19-20 3.7 24.1 20.3 4.8 33.9 16.4 3 3 6.6- 4.8 2.4 2.2 2.3 3. 6. 38.4 1.8 3.2 2.2 4. 25 2 11.6 3. 2.3 43.6 4 6 3 5 31.1 3.2 41. 3.8 1.25 30 5 20-21 20.6 20 3 25.2 16.3 20.8 18.8 18.6 22.3 43.1 21.5 7.6 17.3 14.3 24 6 21 25.2 20.7 17.6 49.6 46.7 11.6 18.6 13.9 49.6 .56 12. 17.6 45 21-22 38. 13.3 63.3 66.3 26.7 7.7 57 7 41. 28 2 30.7 69.7 30.7 41 7 46.3 41. 4.15 29 8 58.3 45.7 36.7 69.7 36.8 85.6 71. 35.8 52.2 21.3 65.6 28.2 4 22 61.8 29.3 54 3 22-23 22.1 9.5 15. 61.9 10. P 3? 3b. 9 24.6 3.92 71.3 14.5 23.2 17 24 8 58.3 13.5 47.2 39.3 22.8 68.3 11.6 74.4 5.311 Tons green matter per acre. Bull. 393 CROP SEQUENCES AT DAVIS TABLE 1— (Continued) Plot No. 50 Check Peas, wheat Wheat, vetch Check Vetch, wheat Wheat, milo, rye — rape Check Milo, rye — rape, wheat Rye — rape, wheat, milo Check Wheat, milo, rye — vetch Milo, rye — vetch, wheat Check Rye — vetch, wheat, milo Wheat-clover con- tinuously Check 13-14 35 3.34 24 22 3.31 24 25.3 56.78 20.5 33.3 29.46 24.6 28.5 24.6 14-15 15. 18.60 6.1i 12.16 15.92 64.12 10.50 4.50! 19.83 13.58 47.28 11.33 20.66 23.66 17.33 21.66 15- 21 67 8.47 54.33 29.35 6.05 28.33 42 22.19 35 42.67 32. 35.66 5-17 30.60 39.33 10. 25 1 27.33 36. 35.66 28 90.3 34 36.5 97.3 39 24.35 28. 17-18 25.5 11.91 51.6 25 5 10' 23.8 13.81 40.1 31.6 35.1 31.6 38 26.3 31.1 18-19 16.9 21.2 1.75 14.5 21.2 8.1 16.1 25.8 60 6 18.8 6.37 35 21.4 56.6 15.8 13.8 19-20 3.4 1.5" 30.9 3. 1.25 28 2 5 6.3 2.25 4. 34.6 3.5 2.12 2.1 3. 20-21 14.2 20.5 25 12.8 22.8 40.9 14.2 3.69 20.1 16.4 43.2 2.75 14.7 18.1 17.8 12.7 21-22 28. 5.12 47.7 25.7 5 25 4.37 26.2 55. 78 8 21.3 7.34 60.8 29 82.3 36.7 27.3 22-23 5.56 15 5 67 42.9 10.5 15.7 16.7 1 Tons green matter per acre. 2 Pasture. The importance of this field of investigation is emphasized by the fact that the major portion of the land area in farms in California is not irrigated and receives a rainfall of less than 20 inches, which falls mainly during the winter months. Under such conditions the eco- nomic diversification of crops is restricted, and the maintainance of the crop producing power of the soil and the conservation of the mois- ture supply present additional difficulties. Plan and Procedure. — A series of plots was laid out in 1913 on land that had been fallowed the previous year but which had grown grain continuously for thirty years or more. It comprises 52 plots each 121 feet long, and 18 feet wide, %o of an acre. There is an open cultivated space of three feet between the plots. The arrange- ment is such that a check plot occurs adjacent to each treatment plot, each third plot being a check and these checks, 18 in all, are planted with wheat continuously. The plan comprises continuous cropping with wheat, oats, barley, rye and milo ; continuous wheat with a legume ; continuous wheat with manure ; wheat and alternate green manure ; rotation including fallow, a four course rotation with and without green manure and several minor trials. Table 1 shows the arrangement of treatments b UNIVERSITY OP CALIFORNIA EXPERIMENT STATION and checks. The yields of grain are expressed in bnshels per acre, and the yield of legumes, forage, etc., in tons of green matter per acre. The sequence of the plots in the table is that of their arrangement in the field This table covers a period of ten years from 1914 to 1923. It is presented for general reference and no comment upon it is necessary here except to point out that the yields from year to year have varied widely, and that very low yields occurred on most plots in 1920. This was a very dry season during Avhich the rainfall (8.94 inches) was only a little more than half the normal. m Fig. 2. — Kough and smooth fallow. The yield of these two plots over a ten-year period has been practically the same, though the rough fallow has dropped a little more rapidly during the second half of the period. See table 9, page 18. The grain crops, including the vetch and peas, were planted in the fall, usually in December, though with occasional variation because of rainfall conditions. The plots summer fallowed were plowed in December and again in March and given two or three cultivations during the early summer (except plot 5, which was left rough or cloddy each year. See fig. 2). The alley-ways between the plots were cultivated during the summer. Sometimes the plots have shown an increased growth along these open ways, but the yield has not been deducted for this because all the plots showed practically the same effect and the results are comparable. Bull. 393] CROP SEQUENCES AT DAVIS 7 The mile- and saccharine sorghum crops were planted in the spring usually about April 15th, thinned to 8 inches in the row and cultivated three to four times during April and May. The rows were spaced three feet which gave six rows to the plot. CLIMATE AND LOCATION Davis is located near the geographical center of the state, 13 miles from Sacramento, and is properly a part of the Sacramento Valley. Its climate, however, with special reference to rainfall, humidity and temperature, is somewhat modified by the conditions of these factors prevailing over the Bay region of San Francisco. This is especially noticeable in regard to temperatures, for northern points in the Sacramento Valley have a higher mean temperature during the growing months than does Davis, and a lower mean temperature during the winter months. Thus, for example, the mean temperature for Davis and Chico are for the months of April to September in- clusive 70.6 and 73.5 degrees, and for the months October to March inclusive, 54 and 52.8 degrees respectively. Occasional northern winds occur at all points in the Sacramento Valley from April to September, and these are sometimes a serious factor in crop production. They are both dry and warm and hence during the early summer months extract a good deal of moisture from the soil, and if the grain is in bloom or filling they effect a deleterious influence on pollination and consequent yields. The relative dryness of these winds is shown by the evaporation from a free water surface, and a single instance may suffice as an illustration. June 14-16, 1917, average temperature, 105; evaporation, .48 inches; pre- vailing wind S.W. June 18-20, 1917, average temperature, 107; evaporation, 1.20 inches; pre- vailing wind N. Rainfall. — Both temperature and rainfall vary widely at Davis, Temperature, however does not exert so great an influence on cereal yields as does rainfall, because during the season of crop growth the temperature is at no time above or below that which is favorable for cereals. The rainfall, however, is a very im- portant factor in crop growth, and its effectiveness is measured not only by the annual amount, but also by its distribution over the season. Since practically all of the rainfall of the valley areas of California falls during the winter months, October to March, the farmer must meet a special set of problems, in moisture conservation and in the maintenance of the optimum physical condition of the 8 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION soil. Because of this peculiarity of the rainfall it semes best to pre- sent the rainfall data according to season rather than by calendar years. (See table 2.) TABLE 2 Eainfall at Davis, 1913-23 July Aug. Sept. Oct. Nov. Dec. Jan. Feb. Mar. Apr. May June Seasonal 12-13 3.43 9.17 4.62 11.01 1.28 .95 .15 4.35 5.01 1.93 5.90 3.59 1.08 .85 1 69 1.14 .61 3.10 .77 1.00 91 .11 .51 .82 .36 .60 2.20 .10 .07 .66 13-14 4.63 .16 .53 .35 .12 7.44 4.75 6.03 4.81 .59 28.70" 20.05 20.88 14.11 9.66 14-15 .71 .03 .46 15-16 ► 93 . 40 Total 16-17 .02 1.7 .49 18.68 Av. 17-13 18-19 4.07 .55 .03 .28 2.19 .31 4.02 1.62 3 2) .53 1.69 2.61 4.39 4.39 7.37 .88 2.49 .37 5.11 2.29 2 62 7.12 .76 .32 5.85 .70 1.54 3.47 1 24 1.47 .02 .83 .30 .40 2.22 19. 40^ 8.94 17.17 16.63 17.86 19-20 .04 20-21 .04 1.46 .21 1.56 .40 .26 .40 .10 \ 80 Total 21-22 16 Av. 22-23 23-24 .35 Normal rainfall for Davis is 17.23 inches. During the first period of these five years there fell 93.4 inches, average 18.68, 1.45 above normal. During the second period of these five years there fell 80 inches, average 16, 1.23 below normal. From this record it may be seen that the rainfall has varied during the ten years mentioned from more than 28 inches for the season 1913- 14 to less than 9 inches for the season 1919-20. This variation in seasonal rainfall has had a marked influence on the crops produced on all the plots of this experiment, and accounts to some extent for the wide variation in yields shown in table 1. During seasons of very heavy rainfall the winter grain and legume crops are injuriously affected by an excess of water in and on the soil, and during seasons of deficient rainfall, spring growth of the grain crops is retarded and the summer growing crops suffer for a lack of moisture, especially on the continuously cropped plots. Seasonal and Spring Rainfall. — Annual winter growing crops are also affected by the amount of precipitation during certain months. Thus, yields in 1914, after an abundant rainfall, were not, for most of the winter grown crops, so heavy as the yields of 1918 after a defi- cient rainfall, and this despite the fact that the 1914 crop had the advantage of early planting (Dec. 1) as compared with late planting (Jan. 24) for the crop of 1918. The figures of table 3 tend to illus- trate this point. These years were chosen because they represent about equal devia- tions from the normal rainfall (17.23). The years 1914 and 1918 Bull. 393" CROP SEQUENCES AT DAVIS illustrate the same tendency, but their rainfall is further from the normal, both above and below. By referring to table 3 it will be noted that in 1916, a year of above normal rainfall, more than 17 inches, or 84 per cent of the total, fell before February 1st. The earlier part of the year had more moisture than was needed because of the nature of the crops and their culture, but this abundance of moisture was largely lost because it was in excess of what could be absorbed and retained. In 1917, a year below seasonal rainfall, about 7 inches or a little less than half of the total precipitation fell after the first of February, while in 1916, a year above normal seasonal rainfall, only 3.28 inches fell after that date. These data with ex- tensive observations tend to emphasize the fact that, granted a reasonable amount and distribution of moisture during the winter months, it is the rainfall of the spring months that makes abundant grain crops. Moreover, late spring rains are nearly always accom- panied and followed by cool, humid weather. This not only retards evaporation and consequently, loss of moisture from the soil, but also prolongs the ripening season of grain crops, and both of these influ- ences enhance the yield of these crops. Thus in 1916 the mean tem- perature for the months March, April and May was 59.6, while that for the same months in 1917 was 56.3, the normal being 58 for the same months. It is not supposed, however, that these yields are consequent upon rainfall alone. There are other factors involved, such as date of planting, shattering, lodging and prevalence of disease, the influence of which it is impossible to evaluate; but it is strongly indicated, at this stage of these experiments, that on these soils and between reason- able dates of planting, the rainfall is the most influential seasonal factor involved in yield of the crops under study. TABLE 3 The Influence of Seasonal Distribution of Eainfall on Yield of Crops Grown Continuously Seasonal rainfall Spring rainfall Feb. -April, inc Wheat— average, all checks (18 plots) Oats continuously, plot 11 Rye continuously, plot 10 Barley continuously, plot 8 Milo continuously, plot 14 Wheat and manure, plot 13 Wheat and legumes, plot 53....... Date of planting winter crops 1916 1917 20.88 14.11 3.28 ,7.02 35.35 39.58 80.00 122.50 12 16 38.60 60.60 74.20 61.67 65.60 42.33 45.33 21.00 24.35 March 5 Dec. 26 10 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION SOILS #//////////, "Hi * '/////&///, wmw< 2 The soils over which these plots are distributed are of two types — fig. 3 — Yolo loam and Yolo silt loam. These soils are described by the Bureau of Soils 1 as follows : ' ' The Yolo loams as mapped in this area comprise the Yolo loam and Yolo silt loam. The Yolo loam consists of a light- brown or brown loam of medium to heavy texture. Gravel is usually absent and the soil as a rule is friable and easily tilled. Considerable variation in the subsoil is noted, but below a depth of 24 inches it often grades into a silty loam or sandy loam of a buff or brownish-yellow color. Clay loam or clay at times constitutes the deeper subsoil and gravelly beds may occur at a depth of 4 to 6 feet long along the site of old stream channels. Altogether the type shows decided variations in the texture of both soil and subsoil, as indicated by borings taken at close range. ' ' The Yolo silt loam is friable in texture. Typically it consists of 36 inches of light-brown or dark grayish- brown silt loam of heavy texture. The soil frequently grades into yellowish-brown substrata of silty clay, clay loam or similar material. "Extreme ranges from layers of sandy loam or sand to clayey beds are encountered in the subsoil of a single boring, but on the whole the group is friable when cultivated and retentive of moisture. On the other hand, the soils are sufficiently open and porous to drain quickly." * ' These soils usually lie a little more elevated than surrounding soil areas and are usually well drained. Alkali seldom occurs in them. They are adapted to a variety of crops, but their yields of grain are notice- ably high during seasons of ample rainfall. ' ' Mechanical Analysis. — The following table gives the results of mechanical analyses of samples of the soil and subsoils of the Yolo loams : Fig. 3_ — The 52 plots in this rotation cover two types of soil, the Yolo loam (L) and the Yolo silt loam (Sil). Each is underlain by a light and heavy phase of subsoil marked L and PI respectively below the line. ' //////// , '■WMM » ///////////, ■■'//////////, *4\W///A