UNIVERSITY OF CALIFORNIA PUBLICATIONS COLLEGE OF AGRICULTURE AGRICULTURAL EXPERIMENT STATION BERKELEY, CALIFORNIA A COMPARISON OF ANNUAL CROPPING, BIENNIAL CROPPING, AND GREEN MANURES ON THE YIELD OF WHEAT BY B. A. MADSON BULLETIN No. 270 August, 1916 UNIVERSITY OF CALIFORNIA PRESS BERKELEY 1916 Benjamin Ide Wheeler, President of the University. EXPEEIMENT STATION STAFF HEADS OF DIVISIONS Thomas Forsyth Hunt, Director. Edward J. Wickson, Horticulture (Emeritus). Herbert J. Webber, Director Citrus Experiment Station; Plant Breeding. Hubert E. Van Norman, Vice-Director; Dairy Management. William A. Setchell, Botany. Myer E. Jaffa, Nutrition. Eobert H. Loughridge, Soil Chemistry and Physics (Emeritus). Charles W. Woodworth, Entomology. Ealph E. Smith. Plant Pathology. J. Eliot Coit. Citriculture. John W. Gilmore, Agronomy. Charles F. Shaw, Soil Technology. John W. Gregg, Landscape Gardening and Floriculture. Frederic T. Bioletti, Viticulture and Enology. Warren T. Clarke, Agricultural Extension. John S. Burd, Agricultural Chemistry. Charles B. Lipman, Soil Chemistry and Bacteriology. Clarence M. Haring, Veterinary Science and Bacteriology. Ernest B. Babcock, Genetics. Gordon H. True, Animal Husbandry. James T. Barrett, Plant Pathology. Fritz W. Woll, Animal Nutrition. A. V. Stubenrauch, Pomology. Walter Mulford, Forestry. W. P. Kelley, Agricultural Chemistry. Elwood Mead, Eural Institutions. H. J. Quayle, Entomology. J. B. Davidson, Agricultural Engineering. H. S. Eeed, Plant Physiology. D. T. Mason, Forestry. William G. Hummel, Agricultural Education. John E. Dougherty, Poultry Husbandry. S. S. Eogers, Olericulture. *Frank Adams, Irrigation Investigations. David N. Morgan, Assistant to the Director. Mrs. D. L. Bunnell, Librarian. division of agronomy J. W. Gilmore W. E. Packard P. B. Kennedy G. W. Hendry E. L. Adams J. A. Denny B. A. Madson L. K. Marshall * In co-operation Office of Public Eoads and Eural Engineering, U. S. D. A. A COMPARISON OF ANNUAL CROPPING, BIENNIAL CROPPING, AND GREEN MANURES ON THE YIELD OF WHEAT* By B. A. MADSON It has been observed that the productive power of the arid and semi-arid soil of the west is more often limited because of an insuffi- cient supply of moisture or because of improper physical and biological conditions than because of a lack of certain fertilizing elements. This is especially true where dry farming is practiced, in which case the cereals constitute the principal crop grown. In the more humid sec- tions, where water is usually abundant, corresponding defects in physical and biological conditions may generally be corrected by the use of systems of crop rotation. Under arid conditions the develop- ment of a comprehensive system of crop rotation is rendered somewhat difficult because of the limited number of crops adapted to these conditions. Some modification of this character, however, is necessary in the system of grain farming in California, as evidenced by the fact that wheat production in the state has decreased more than 80 per cent during the past ten years, a condition which can be attributed largely to the deleterious effects of continuous one-sided cropping. To overcome this deficiency of crops, a year of fallow and addition of organic matter to the soil by the use of cover crops have been ad- vocated. The year of fallow is recommended primarily as a moisture- conserving measure, to make possible an adequate supply of moisture in the soil for a maximum crop at all times. The use of the cover crop, on the other hand, is recommended as a means of maintaining the supply of humus which is lost so rapidly by oxidation under con- tinuous cultivation and cropping. Humus appears to be necessary to keep the soil in good tilth, to stimulate bacterial activity and to main- tain its maximum moisture-holding capacity. One or both of these practices, together with proper cultivation, have been found under many conditions not only to aid materially in maintaining the pro- ductivity of dry-farm soils but in many cases to be absolutely essential * The experiment discussed in this publication was outlined by and executed under the direction of Dr. G. W. Shaw, in charge of the Agronomy work until 1913. The field work was conducted under the supervision of Mr. A. J. Gaumnitz, in charge of the experimental work at Davis during the same period of time. 4 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION to successful crop production. On the sandy soils near Ceres, in the San Joaquin Valley, Shaw 1 found that by the use of the summer fallow alone the yield of wheat could be more than doubled, while by the use of green manure crops, combined with the summer fallow, the yield was increased from 230 to 340 per cent, depending upon the amount of organic matter added. Necessarily, however, the effect of these treatments will vary not only with the total precipitation and its seasonal distribution but more particularly with the type and char- acter of the soil. In order to secure some information as to the value of these treat- ments under Sacramento Valley conditions, a biennial cropping ex- periment was begun in 1907 on the University Farm at Davis, a portion of which was previously discussed by Shaw in the bulletin above cited. This project was designed to show the effects of fallow and of various green manure crops in combination with the fallow, as compared with continuous cropping on the yield of wheat. The results obtained in this investigation since the publication of Professor Shaw's bulletin are presented in this bulletin, with such discussions as these may suggest. Climate. — The climate at Davis is usually classed as semi-arid. The normal precipitation is approximately 17.32 inches, the greater portion of which falls during the winter months, while the months of June to September are generally absolutely rainless. There is, how- ever, a very wide variation in the seasonal precipitation, as indicated by the subjoined table. This fact and the frequent occurrence of hot north winds during the spring and summer months render moisture- conserving measures imperative. TABLE I Eainfall at Davis Seasons, 1907-08 1908-09 1909-10 1910-11 1911-12 1912-13 1913-14 Inches 13.16 22.48 11.35 23.18 9.41 8.84 28.70 Soil. — The soil type upon which this experiment was undertaken is technically known as Davis silt loam. The surface soil is a rather heavy silt loam varying in depth from four to five feet. It is, how- ever, in fair physical condition, is relatively easy to work, and has a maximum water-holding capacity of approximately 30 per cent, ac- cording to field determinations. This surface soil is underlaid by a layer of sand six to eight inches in thickness and this in turn under- laid by a heavier clay loam. i Calif. Bulletin No. 211, p. 267. EFFECT OF CROPPING SYSTEMS ON WHEAT O The project consisted of fourteen one-tenth acre plats quite uni- form in character and included five trials with various green manure crops as compared with bare fallow and with continuous cropping. Each test was made in duplicate, so that of the biennial cropped plats one plat out of each series was cropped to wheat every year. During the summer of 1907 all plats were fallowed in order to disintegrate the plow sole and put the soil in as good physical condition as possible. This was deemed advisable inasmuch as the field had been cropped to grain for a number of years prior to its being used for experimental purposes. Treatment of Plats. — During the subsequent year all plats received the same cultural treatment as far as conditions would permit. Plow- ing was done in the late fall or early winter, as soon as the rain had sufficiently moistened the ground. The surface was then worked down to a good seed bed and the wheat and the green manure crop seeded with a drill. The fallow plats were allowed to lie in the rough con- dition until spring, when the weed growth was destroyed and the surface worked down to an even mulch; this mulch was maintained throughout the summer by an occasional cultivation with either a harrow or a disc. On the green manure plats the cover crop was turned under in the spring, after which the surface was worked down to a mulch; this mulch was maintained throughout the summer in exactly the same manner as on the fallow plats, with one exception. Plats Nos. 38 and 39, upon which horse beans were grown as a cover crop, were plowed in the spring, worked down and planted to Kaffir corn during a part of the experiment. When the wheat crop was removed from the plats in the summer the stubble was immediately disced, the mulch thus formed aiding materially in checking the loss of moisture from the soil by direct evaporation. The treatment of the various plats and the yields ob- tained are given in Table II. In comparing the data presented in Table II it will be observed that the average yield of the two continuously cropped plats, Nos. 30 and 37, namely, 21.75 bushels per acre, is slightly higher than the average of any of the biennial cropped plats. Of the biennial cropped plats, Nos. 33 and 34, on which horse beans and fenugreek were grown as a cover crop, gave the highest returns. In all fairness, however, it must be said that the horse beans failed to produce much growth, so that their effect as a green manure crop was practically nothing. The fenugreek, however, made a fair growth, but had occasion to influence but one of the six wheat crops. 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Perhaps the most striking fact revealed by the data in Table II is the rapid decrease in yield of the continuously cropped plats during the progress of the experiment. In the case of the biennial cropped plats there appears to be no consistent change in productivity^ with the exception of plats Nos. 40 and 41, upon which rye and vetch were employed as a cover crop. In fact, it is evident that had the experi- ment continued a few years longer all the biennial cropped plats, with the possible exception noted, would have surpassed in yield the con- tinuously cropped plats. It must also be remembered that all the plats were fallowed during the summer of 1907, prior to the beginning of the experiment, so that the condition on plats Nos. 30 and 37, for the first season at least, was identical with that of the biennially cropped plats. The results clearly indicate that the year of fallow very markedly affected the growth on the continuously cropped plats for at least two seasons. This is especially significant considering the short duration of the experiment. Furthermore, one plat out of each series of the biennial cropped plats was not cropped for the two seasons, 1906-07 and 1907-08, a condition which might tend to vitiate the results somewhat, though the effect, TABLE III Eesults of the Last Four Years of the Biennial Cropping Experiment Plat No. 1909-10 1910-11 1911-12 1912-13 Total 4 yr. Yield per acre, bu. Av. annual Grand yield per average, acre, bu. bu. 30 Ck. 21.58 10.33 10.83 3.17 45.91 11.48 11.48 31 28.00 Fallow 44.83 Fallow 72.83 18.21 ► 17.67 32 Fallow 24.75 Fallow 43.83 68.58 17.14 33 34 Horse beans 28.91 34.83 Horse beans Fenugreek 41.33 40.67 Fenugreek 75.50 70.56 18.87 17.56 1 18.21 35 Field peas 34.33 Field peas 31.42 65.75 16.44 I 16.71 36 29.25 Field peas 37.66 Field peas 67.98 16.98 37 Ck 22.41 11.00 6.66 5.08 43.18 11.29 11.29 38 Horse beans j ' Kafir 28.58 Horse beans 28.58 57.16 14.29 > 16.83 39 31.83 Horse beans Kafir 45.66 Horse beans 77.49 19.37 40 Rye & vetch 29.00 Rye & vetch 9.07 38.17 9.54 > 10.34 41 32.08 Rye & vetch 12.50 Rye & vetch 44.58 11.14 42 Burr clover 26.16 Burr clover 23.17 49.83 12.46 1 43 41.41 Burr clover 39.50 Burr clover 79.91 19.98 { 16.22 8 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION if any, is less apparent. Again, on the green manure plats the treat- ment in some cases did not become effective until the third year, so that only the last four years show a true comparison of the various treatments. On the whole, therefore, it would probably be better to regard the first two seasons ' results as preliminary and to include only the last four years 7 results in comparing the merits of the various treatments. The yields considered on this basis are given in Table III. The results of the last four years have been decidedly in favor of biennial cropping, with the exception of plats Nos. 40 and 41, on which rye and vetch were employed as a cover crop. The difference in yield, however, between the continuously cropped plats and the biennially cropped plats is too great to be attributed to any other factor than the effect of the treatment given. Unfortunately no determinations were made on the green manure plats to ascertain whether or not there was any relation between the total weight of organic matter added to the soil and the yield produced. Attention must be called to the fact, however, that the green manure plats, Nos. 40 and 41, which gave the lowest average yield, not only for the last four years but throughout the experiment were the only ones upon which a cereal was employed as a cover crop. It is quite probable that the total organic matter added was greater when rye was used as a part of the cover crop than when a legume alone was used. This would seem to indicate either that the growth of a larger cover crop tended to reduce correspond- ingly the water content of the soil, thereby affecting the yield of the following crop, or that the cereal (rye) exerted some influence on the soil which affected the growth of the succeeding crop unfavorably. On the whole, in comparing the effect of the various cover crops with bare fallow the results would indicate that the cover crop was harmful rather than beneficial. However, plats Nos. 33 and 34, upon which horse beans and fenugreek were grown as cover crops, the former being almost a total failure, gave a slightly higher yield than the bare fallow plats. Even plats Nos. 38 and 39, upon which the cover crop of horse beans was followed by Kafir corn during the first four years, gave as large a yield of wheat throughout the experiment as did the field peas and bur clover plats. "While the Kafir did not mature in most cases, the yield of forage varied from four to eight tons per acre, the growth of which must have caused a considerably greater draft upon the moisture supply of the soil than did the cover crops. Furthermore, the Kafir and other sorghums are generally considered to be "hard" on the soil, greatly reducing the yield of the following cereal crops. The rapid and consistent decrease in yield of both the continuously cropped plats is striking. At first it would appear that this decrease EFFECT OF CROPPING SYSTEMS ON WHEAT 9 might be accounted for by an insufficient supply of moisture. For the last two crops at least this is doubtless true, as the rainfall was very low, the combined precipitation for the two seasons being only 18.25 inches. On the whole, however, there seems to be no close cor- relation between the average yield of the continuously cropped plats YEAE.S W-08 1908-09 1909-10 1910-11 FIG. 1_ CURVES SHOWING THE fcELATIOM 5ETWEE/1 THE RAfMFALL AMD THE YIELDS Oh THE PLATS CROPPED TO WHEAT CO/NTIMUOU5LY and the seasonal precipitation, as is shown by figure 1, the yield de- creasing continually while the precipitation was decidedly variable. It is further worthy of note that in 1913, the second of two dry years, the yield on plat No. 32, which was fallowed the previous season, was 43.83 bushels of wheat per acre, while plat No. 33, to which a cover 10 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION crop of fenugreek had been added the previous season, yielded 40.67 bushels of wheat per acre. The results obtained the succeeding season (1914) further strengthened the belief that water alone was not the limiting factor. While the experiment was technically closed at the end of the 1913 season, all the plats, with the exception of No. 32, were cropped to some cereal the next year, the results of which are given in Table IV. Plats Nos. 30 and 31 were both planted to the same variety of wheat. It will be noted that the yield of plat No. 30, which has been cropped to wheat continuously, was only 11.17 bushels per acre in spite of the fact that the seasonal precipitation was 28.70 inches. TABLE IV Yield of Cereals on the Plats of the Biennial Cropping Experiment, Season of 1914 Yield Plat No. Treatment, 1913 Crop grown, 1914 per acre, bu. 30 Wheat Bobs Wheat 11.17 31 Fallow Bobs Wheat 25.42 32 Wheat Fallow 33 Wheat Beldi Barley 190 58.20 34 Fenugreek Beldi Barley 190 65.20 35 Wheat Imp. Beldi Bar. 1601 53.80 36 Field Peas Chevalier Bar. 5865 65.60 37 Wheat Chevalier Bar. 5865 29.40 38 Wheat Chevalier Bar. 5865 52.80 39 Horse Beans Burt Oats 293 40.00 40 Wheat Burt Oats 293 44.69 41 Eye and Vetch Burt Oats 293 47.66 42 Wheat white Aust. Wh. 12113 28.16 43 Burr Clover White Aust. Wh. 12113 24.37 Plat No. 31, which had been fallowed the previous season, yielded 25.42 bushels of wheat per acre. The other plats in the experiments were cropped to various cereals, so that an exact comparison cannot be made. The results on the other continuously cropped plats and the two adjoining plats, Nos. 36 and 38, which were seeded to Chevalier barley, are also of interest. Plat No. 37, which had been continuously cropped to wheat, yielded only 39.4 bushels of barley per acre. Plat No. 38, cropped to wheat the previous season, which was preceded by a cover crop of horse beans, yielded 52.8 bushels per acre, and plat No. 36, upon which had been grown a cover crop of field peas in 1913, yielded 65.6 bushels of barley per acre. It does not seem probable that in either instance the difference in yield could be attributed to a EFFECT OF CROPPING SYSTEMS ON WHEAT 11 difference in moisture supply, as all plats were abundantly supplied with moisture throughout the growing season. In fact, the heavy spring rains kept the soil nearly saturated until the crop was fully headed. From the data obtained it would certainly appear that some factor other than the lack of moisture was responsible for the decline in yield under continuous cropping. Considering the results obtained on the plats in which rye was used as a part of the cover crop, it would appear that the cereal exerted some unfavorable influence upon the succeeding grain crop. Whether this condition is due to some toxic substance left in the soil, to the development of fungi, as maintained by Bolley, or to some effect of the fibrous root system on the physical, chemical or biological condition of the soil is still undetermined. The results, however, would suggest that some effect of this character was the real limiting factor. The fact that most of the plats upon which a legum- inous cover crop had been grown gave a lower yield than the bare fallow plats might be explained on the basis of moisture, the cover crop using a portion of the moisture which might otherwise have served to supply the wheat crop. This explanation seems plausible, since the difference in yield during seasons of high rainfall was very slight, the greatest difference occurring during the drier seasons. It would seem, therefore, that while the addition of organic matter may be of value, its beneficial effect is not sufficient to compensate for the water used in its growth, nor does the soil appear to be seriously lacking in any constituent which the cover crop might add. From an economic point of view, the bare fallow unquestionably produced the greatest net returns per acre. The cost of maintaining a good summer fallow, including plowing and the necessary cultiva- tion, is usually slightly less than the cost of producing a crop of wheat. The annual increase in yield of 6.29 bushels per acre, which was ob- tained from the fallow plats, is therefore largely clear gain. In other words, to be economically a success, the fallow plats would have to produce only twice as large yields every alternate year as was pro- duced by the continuous cropped plats annually, whereas the actual average production of the fallow plats every two years was 35.35 bushels per acre, as compared with 11.38 bushels per acre, which was the annual production of the plats cropped continuously. In the case of the green manure plats, while the yields were consid- erably larger than those obtained under continuous cropping, they were, on the whole, somewhat lower than the yield obtained on the fallow plats. Furthermore, the cost of producing and handling the green manure crop is at least 50 per cent greater than the cost of 12 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION maintaining the fallow, including as it does the cost of putting in the crops, the cost of the seed and additional plowing in the spring, be- sides the same summer cultivation that is given to the fallow. On the whole, therefore, the actual economic returns attending the use of a green manure crop is but slightly greater than those obtained under a system of continuous cropping. EFFECTS ON THE SOIL It is usually maintained that the addition of organic matter to the soil by the use of green manure crops will aid in increasing its humus content. In humid sections this is true, and experiments have shown that the plowing in of a cover crop has increased the humus content in some cases 1 per cent. Under arid conditions, however, the increase in humus content by the use of a cover crop has been found in most instances to be very slight. As has been pointed out by Scofield, under arid conditions the low moisture content of the surface soil, together with high temperature and high degree of aeration, tends to stimulate direct oxidation, rather than humification, so that in a short time the larger proportion of the organic matter may be lost without adding materially to the humus content of the soil. Hilgard also states that "in the absence of a sufficient degree of moisture to co- operate with the agencies of humification the final results in the soil is practically the same as in the 'fire fanging' of dung. The organic matter is almost wholly destroyed by direct oxidation with or without the aid of minute organisms, leaving essentially only the ash behind to be reincorporated with the soil." Unfortunately no systematic studies were made to determine the effect of the various treatments upon the soil in the experiments at Davis. A few tests were made in the spring of 1913 by Mr. S. E. Ooodall, at that time a senior student in the department of agriculture, with a view to determining the effect of the various treatments on the humus content of the soil, as well as on the nitrogen content of the humus. The results thus obtained are given in Table V. The soil samples upon which these determinations were made were taken in January, about ten months after the last cover crop had been plowed in. The results indicate that no increase in humus content occurred following the application of the green manure crop. While a variation of .28 per cent of humus was obtained in the first foot, both extremes occurred on plats to which the last cover crop had been added nearly two years previous. The difference in the average humus con- tent for the various treatments is too slight to be significant. The fact that the humus content of the first foot is slightly less on the EFFECT OF CROPPING SYSTEMS ON WHEAT 13 1913 TABLE V Humus and Humu s Nitrogen Content of Soils, January, Plat No. Per cent of H A umus Per cent Nitrogen in Humus A 1st ft. 2nd ft. 3rd ft. 1st ft. 2nd ft. 3rd ft. 30 1.12 .86 .62 15.0 11.2 19.4 31 1.02 .90 .54 8.5 8.5 13.5 32 • .98 .90 .54 10.6 10.6 14.7 33 1.10 .90 .54 9.5 7.5 10.4 34 .94 .82 .52 8.5 9.8 10.4 35 1.06 .88 .72 9.4 11.2 12.2 36 .94 .80 .60 10.1 9.8 10.7 37 1.06 .80 .64 8.0 9.9 11.7 38 1.14 .94 .70 10.3 10.8 13.4 39 1.18 1.02 .62 9.9 10.5 16.4 40 1.18 .90 .62 10.2 8.9 9.6 41 1.10 .96 .66 9.5 7.3 10.1 42 1.14 .70 .54 8.8 10.0 12.2 43 1.22 .74 .56 8.4 8.9 8.6 Av. of continuously- cropped plats, Av. of fallow plats, 1.09 1.00 .83 .90 .63 .54 11.5 9.5 10.5 9.5 15.5 14.1 Av. of green manure plats, 1.10 .86 .61 9.4 9.5 11.4 fallow plats than on the other plats corroborates the usual observations as to the effect of summer cultivation on the oxidation of the humus. In the nitrogen content of the humus, it is not clear just why the humus in the soil of the continuously cropped plats should be higher in nitrogen than that of the other plats. The most probable expla- nation would be that less of the organic matter left in the soil as wheat roots was lost by direct oxidation than in the case of that applied as cover crops. In the latter case, in the process of oxidation it is quite likely that a large portion of the nitrogen was lost as well. Another possibility that suggests itself is that a more rapid rate of nitrification occurred when the green material had been added than on land that had been cropped, so that a larger portion of the nitrogen was changed to the nitrate form. In the absence of nitrate determinations, how- ever, this can only be assumed. From the results obtained in this experiment it would appear that soils such as those at Davis contain sufficient organic matter to meet the demands of a normal crop. While the addition of organic matter by the use of a cover crop may tend to stimulate bacterial activity and the liberation of plant food, the benefit thus derived is not sufficient to counterbalance the draught made upon the soil moisture by the growth of the crop. Furthermore, because of the rapid oxidation 14 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION which takes place in the soil the cover crops did not increase the humus content, but were entirely lost before the next wheat crop was grown. On the other hand, the bare fallow greatly stimulated the crop- producing power of the soil, though it is evident that if long continued the humus content will be seriously depleted. It will doubtless, there- fore, eventually be necessary to add organic matter in some form if the crop-producing power of these soils is to be permanently main- tained. It would also appear that there was considerable difference in the comparative value of the various crops for green manure purposes, though the exact reason for this is not clear. Again, while the highest economic returns were obtained from the bare fallow, it does not hold that biennial cropping as practiced in this experiment is necessarily productive of the greatest returns. It is quite likely that from an economic point of view the use of the fallow every third or even every fourth year would give larger total returns over a long period of time than biennial cropping. As an integral part of a dry-farm rotation, however, its value can not be questioned. CONCLUSIONS 1. The marked decline in wheat production in California has been caused by the deleterious effects of continuous one-sided cropping, together with inadequate cultivation. 2. Under a system of continuous cropping to wheat the yield de- creases very rapidly to a point below profitable production. 3. The year of fallow is one of the most effective means of retaining the productive power of semi-arid soils. 4. The use of green manure crops increases the productivity of the soil, but not to the same extent as does the bare fallow. 5. There appears to be a decided difference in the effect of the various cover crops. Apparently a cereal should not be used as a cover crop in a cereal rotation on soils such as those on the University Farm at Davis. 6. The organic matter added to the soil by the cover crop appears to be practically lost by oxidation the following summer. 7. The frequent use of the fallow will probably hasten the depletion of the humus content of the soil, even though it greatly increases its productive power. 8. The use of cover crops, even if they be legumes, does not seem to increase the content of humus or of humus nitrogen in the soil to any appreciable extent; the favorable effects of cover crops that are frequently observed must, therefore, be attributed to other causes than an increase of the humus in the soil. STATION PUBLICATIONS AVAILABLE FOE FREE DISTRIBUTION REPORTS 1897. Resistant Vines, their Selection, Adaptation, and Grafting. Appendix to Viticultural Report for 1896. 1902. Report of the Agricultural Experiment Station for 1898-1901. 1903. Report of the Agricultural Experiment Station for 1901-03. 1904. Twenty-second Report of the Agricultural Experiment Station for 1903-04. 1914. Report of the College of Agriculture and the Agricultural Experiment Station, July, 1913-June, 1914. 1915. Report of the College of Agriculture and the Agricultural Experiment Station, July, 1914-June, 1915. No. 168. 169. 178. 184. 185. 195. 207. 208. 212. 213. 216. 225. 227. 230. 241. 242. 246. 248. 249. 250. Observations on Some Vine Diseases in Sonoma County. Tolerance of the Sugar Beet for Alkali. Mosquito Control. Report of the Plant Pathologist to July 1, 1906. Report of Progress in Cereal Investi- gations. The California Grape Root-worm. The Control of the Argentine Ant. The Late Blight of Celery. California White Wheats. The Principles of Wine-making. A Progress Report Upon Soil and Cli- matic Factors Influencing the Com- position of Wheat. Tolerance of Eucalyptus for Alkali. Grape Vinegar. Enological Investigations. Vine Pruning: in California, Part I. Humus in California Soils. Vine Pruning in California, Part II. The Economic Value of Pacific Coast Kelps. Stock-Poisoning Plants of California. The Loquat. BULLETINS No. 251. 252. 253. 254. 255. 256. 257. 261. 263. 265. 266. 267. 268. 269. 270. 271. Utilization of the Nitrogen and Organic Matter in Septic and Imhoff Tank Sludges. Deterioration of Lumber. Irrigation and Soil Conditions in the Sierra Nevada Foothills, California. The Avocado in California. The Citricola Scale. Value of Barlev for Cows Fed Alfalfa. New Dosage Tables. Melaxuma of the Walnut, "Juglans regia." Citrus Diseases of Florida and Cuba Compared with Those of California. Size Grade for Ripe Olives. Cottony Rot of Lemons in California. A Spotting of Citrus Fruits Due to the Action of Oil Liberated from the Rind. Experiments with Stocks for Citrus. Growing and Grafting Olive Seedlings. Phenolic Insecticides and Fungicides. A Comparison of Annual Cropping, Biennial Cropping, and Green Ma- nures on the Yield of Wheat. Feeding Dairy Calves in California. CIRCULARS No. No. 65. The California Insecticide Law. 134. 69. The Extermination of Morning-Glory. 135. 70. Observations on the Status of Corn 136. Growing in California. 13 7. 76. Hot Room Callusing. 138. 80. Boys' and Girls' Clubs. 139. 82. The Common Ground Squirrels of California. 83. Potato Growing Clubs. 140. 106. Directions for Using Anti-Hog Cholera Serum. 107. Spraying Walnut Trees for Blight and 141. Aphis Control. 108. Grape Juice. 142. 109. Community or Local Extension Work by the High School Agricultural De- 143. partment. 113. Correspondence Courses in Agriculture. 144. 114. Increasing the Duty of Water. 145. 115. Grafting Vinifera Vineyards. 117. The Selection and Cost of a Small 146. Pumping Plant. 118. The Countv Farm Bureau. 147. 121. Some Things the Prospective Settler 148. Should Know. 149. 124. Alfalfa Silage for Fattening Steers. 150. 126. Spraying for the Grape Leaf Hopper. 151. 127. House Fumigation. 152. 128. Insecticide Formulas. 129. The Control of Citrus Insects. 153. 130. Cabbage Growing in California. 131. Spraying for Control of Walnut Aphis. 154. 132. When to Vaccinate against Hog Cholera. 155. 13 3. County Farm Adviser. Control of Raisin Insects. Official Tests of Dairy Cows. Melilotus Indica. Wood Decay in Orchard Trees. The Silo in California Agriculture. The Generation of Hydrocyanic Acid Gas in Fumigation by Portable Ma- chines. The Practical Application of Improved Methods -of Fermentation in Califor- nia Wineries during 1913 and 1914. Standard Insecticides and Fungicides versus Secret Preparations. Practical and Inexpensive Poultry Ap pliances. Control of Grasshoppers in Imperial Valley. Oidium or Powdery Mildew of the Vine. Suggestions to Poultrymen concerning Chicken Pox. Jellies and Marmalades from Citrus Fruits. Tomato Growing in California "Lungworms" Lawn Making in California. Round Worms in Poultry. Feeding and Management of Hogs. Some Observations on the Bulk Hand- ling of Grain in California. Announcement of the California State Dairy Cow Competition, 1916-18. Irrigation Practice in Growing Small Fruits in California. Bovine Tuberculosis.