PNITER8ITY OF CALIFOBgIA PUBLICATIONS COLLEGE OF AGRICULTURE AGRICULTURAL EXPERIMENT STATION BERKELEY, CALIFORNIA RICE IRRIGATION MEASUREMENTS AND EXPERIMENTS IN SACRAMENTO VALLEY 1914-1919 By FRANK ADAMS BULLETIN No. 325 September, 1920 UNIVERSITY OF CALIFORNIA PRESS BERKELEY 1920 David P. Barrows, President of the University. EXPERIMENT STATION STAFF HEADS OF DIVISIONS Thomas Forsyth Hunt, Dean. Edward J. Wickson, Horticulture (Emeritus). Walter Mulford, Forestry, Director of Resident Instruction. C. M. Haring, Director of Agriculture Experiment Station; Veterinary Science. B. H. Crocheron, Director of Agricultural Extension. Hubert E. Van Norman, Vice-Director; Dairy Management. James T. Barrett, Acting Director of Citrus Experiment Station; Plant Pathology. William A. Setchell, Botany. Myer E. Jaffa, Nutrition. Ralph 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 Fruit Products. Warren T. Clarke, Agricultural Extension. John S. Burd, Agricultural Chemistry. Charles B. Lipman, Soil Chemistry and Bacteriology. Ernest B. Babcock, Genetics. Gordon H. True, Animal Husbandry. Fritz W. Woll, Animal Nutrition. W. P. Kelley, Agricultural Chemistry H. J. Quayle, Entomology. Elwood Mead, Rural Institutions. H. S. Reed, Plant Physiology L. D. Batchelor, Orchard Management. J. C. Whitten, Pomology. Frank Adams, Irrigation Investigations. C. L. Roadhouse, Dairy Industry. R. L. Adams, Farm Management. F. L. Griffin, Agricultural Education. John E. Dougherty, Poultry Husbandry W. B. Herms, Entomology and Parasitology. L. J. Fletcher, Agricultural Engineering. Edwin C. Voorhies, Assistant to the Dean. division of irrigation investigations (In cooperation with Bureau of Public Roads, U. S, Department of Agriculture.) Frank Adams. F. J. Veihmeyer. S. H. Beckett. II. A. Wadsworth. RICE IRRIGATION MEASUREMENTS AND EXPERIMENTS IN SACRAMENTO VALLEY 1914-1919 By FKANK ADAMS CONTENTS PAGE Cooperation 48 Measurements of Use of Water 48 Comments on Duty of Water Tables 50 Evaporation 56 Experiments at Biggs and Norman 58 Rice Growing and Alkali Injury 65 Irrigation and Water Grass 66 Summary 66 Appendix , 69 In May, 1917, this station published a bulletin* describing Califor- nia rice irrigation practice, and methods of preparing land for rice irrigation, and also giving results of measurements of the amounts of water used in 1916 on eighteen typical Sacramento Valley rice fields, and of cooperative experiments in rice irrigation from 1914 to 1916 conducted at the Biggs Rice Field Station. Further measure- ments of use of water were made in 1917 and 1918, and the experi- ments at Biggs have been continued through 1919. In addition, the Biggs experiments were duplicated during 1918 and 1919 on a differ- ent type of soil on the west side of Sacramento Valley, on the Spalding Ranch, near Norman. This brief supplementary bulletin has been prepared to summarize and discuss both the earlier and later meas- urements and experiments. To the extent available, also, gross meas- urements of use of water on rice fields, taken from operation reports of canal companies and from measurements of diversions from Sacra- mento River in 1919 by the State Department of Engineering, in part in cooperation with this station, are reported in the appendix. * Univ. Calif., Coll. Agr., Agr. Exp. Sta. Bull. 279, Irrigation of Rice in Cali- fornia, bv Raich D. Robertson. 50 UNIVERSIY OF CALIFORNIA EXPERIMENT STATION Table II Summary of Measurements of Duty of Water in Rice Irrigation in Sacra- mento Valley, Seasons of 1916, 1917, and 1918, Grouped by Soil Types and Arranged in Order of Depth of Water Applied Soil classification Number of full season observations Total area included in observations, acres Average net depth of water applied, feet Average area served during full season per cu. ft. per sec, acres Capay clay Willows clay adobe Willows clay Stockton clay adobe Sacramento clay Tehama clay loam and clay Vina clay loam Willows loam and clay or clay adobe Madera clay loam, etc Willows loam San Joaquin loam Total or average 2 7 7 12 4 2 1 2 1 2 3 355 8,477 5,057 2,877 4,653 267 302 71 172 122 51 3.94 4.22 9.38 10.94 81 72 70 60 59 43 37 37 37 36 30 43 22,404 4.89 66 COMMENTS ON DUTY OF WATER TABLES The chief factors that usually affect and determine the duty of water in irrigation of orchards or field crops in any given locality — openness of the soil to receive and its ability to absorb water, crop, preparation of the land for irrigation, slope of land, irrigating "head" or stream available, length of growing season, and care with which water is applied — affect and determine the duty of water in rice irrigation in somewhat different measure. In the first place, for best results, rice must have sufficient water, in "heads" or streams of sufficient size, to permit of one initial flood- ing five to ten inches deep over the entire area and three to six flush- ings to keep the soil fairly moist during germination and prior to beginning of the submergence period; that is, for from 40 to 50 days, or longer, depending upon the growing weather during this period and upon how well the rice has been seeded. In 16 cases out of the 43 listed in table I this preliminary irrigation period exceeded 50 days. Excepting during the period of beginning submergence and bringing the submergence to the required depth, the period of initial flooding is the time of largest need if the irrigation is to be accom- plished satisfactorily. Bulletin 325 RICE irrigation MEASUREMENTS 51 Second, the crop must be kept submerged from about 30 days, more or less, after emergence of the plants above the ground until the crop has been made, ranging from about 90 days for the earlier maturing varieties to about 110 to 130 days, or more if the season is cold, in the case of the Wataribune variety that has been so largely grown in California. Obviously, under any given condition of soil and preparation, the shorter this period of submergence the smaller the total quantity of water used during the season. Fig. 1. — First flooding of a new rice field after seeding. Difference in elevation between contours or cheeks is about three inches. Third, under any given condition of flushing and submergence, it is clear that rice soil will require water in direct proportion to its imperviousness. From a water standpoint, therefore, that soil is most satisfactory for rice growing that loses the least water by percolation through it; and that soil will show the lowest duty (the largest use) which, because of its loamy texture, permits the most water to pass through it and into the subsoil. Fourth, the near proximity of deep drains and also poorly made outside levees exert a far greater influence on water duty in rice grow- ing than in the case of other crops, due to the longer period — 3 to 4 months — the irrigation water is held on the land during the sub- mergence period; and, furthermore, evaporation is a greater factor than with other crops. 52 UNIVERSIY OF CALIFORNIA EXPERIMENT STATION Finally, limited observations indicate that instead of requiring a more careful use of water as in the case of ordinary cultivated crops, alkali lands utilized for rice growing require a somewhat greater quantity than lands free from alkali because of needing more frequent irrigations during the pre-submergence period and of the further need of more constant circulation of water through the checks to carry off the alkali washed out from the surface soil. Thus, in rice irrigation the amount of water used — the duty of water — needs to be considered from a standpoint quite different from the standpoint of orchard or field crop irrigation. Excepting during the period prior to submergence, neither the capacity of the soil to receive and absorb water in single irrigations, nor the length of irri- gation runs, nor even the surface preparation of the land will govern the total seasonal use as much as the imperviousness of the soil during submergence, the ability of the outside levees to retain water, the length and warmth of growing season, and the maturing period of the variety grown. With the return of a normal price for rice, the cost of water will also be a governing factor that at present is apt to be lost sight of. Table I is particularly instructive in showing the wide variation in use within the different soil classifications. In practice newly pre- pared and seeded fields require more water than during the one to three subsequent seasons rice is grown before resting the land. This obviously is due to the settling of the levees, particularly the outside levees, during and after the first season, and also to the compacting of the surface soil after the deeper plowing usually given when the field is first seeded or during the seasons the fields are fallowed to get rid of water grass. This is borne out in numerous instances included in the table as may be seen by comparing use on the same fields for different seasons. Other factors, such as a more plentiful water supply the subsequent seasons, may, however, alter this, although other things being equal, the rule holds true. Another interesting fact brought out by table I is the consider- able variation in the full length of the growing season, the shortest shown being 135 and the longest 189 days. Crop yields, not included in the table, were obtained in the case of all of the fields listed and these have been scrutinized for any definite relation they may have to the quantity of water used. Since water grass, however, is a governing factor in yields of rice, given ample water, and since this pest was present more or less in all second and third year fields under observation, no clear relation was found Bulletin 325 RICE irrigation measurements 53 except where there was a definite shortage of water. But this is clear from the crop data: The best yields were not always obtained where the most water was used, nor the poorest yields where the least was used, but generally speaking, just the contrary. For instance, of nine fields producing 40 sacks or more per acre, one used under 4 feet in depth, three used between 4 and 5 feet, two used between 5 and 5.5 feet, one (with a large drain adjacent) used 7.69 feet, one 8.13 feet, and one 9.07 feet; while of six fields producing under 20 sacks per acre, four received gross applications in excess of 12 feet in depth, the other two in excess of 7 feet in depth. Four of the fields having this low yield and excessive use had loam soils; one, however, with a yield of only 17 sacks, was damaged by water grass and ducks. The regrouping of the data by soil classifications, as presented in table II, makes the fact clear that the best duty of water in rice irri- gation in Sacramento Valley, so far as observations have gone, is found on the clays and clay adobes of the Capay, Willows, Stockton, and Sacramento series. So far as water controls, therefore, the data presented indicate that over long periods the permanent rice growing industry in Sacramento Valley will mainly be found on these soils. The rapid encroachment on the unregulated flow of water in Sacra- mento Valley, especially of Sacramento River, has already made the scarcity of summer water the limiting factor in rice growing, and it is obvious that those soils will most likely be retained in this crop that require the least water for successful rice culture. While measurements on a number of fields, such as are listed above, are necessary to ascertain the actual use of water, actual requirements can be more satisfactorily determined on a few fields where satisfactory physical conditions are present and where water is used without waste. At least one entirely satisfactory field is included in the table in the E. L. Adams field of 39.5 acres, which adjoins the Biggs Rice Field Station, and on which measurements were made from 1914 to 1917. This field was properly handled throughout, kept free from water grass, and ample water used but none wasted. The principal data for this field are regrouped in table III below with additional data added. This indicates better than any other field under observation what can be accomplished on such soil as Stockton clay adobe, which comprises a large area of rice soil in Sacramento Valley, and taken in connection with the data for the other fields listed, justifies the conclusion that on the best rice soils, an annual use of five acre-feet per acre is sufficient. 54 UNIVERSIY OF CALIFORNIA EXPERIMENT STATION Table III Results of Measurements of Use of Water on E. L. Adams Rice Field, Near Biggs, 1914-1917. Area, 39.5 Acres; Soil, Stockton Clay Adobe. Full irrigation season Net depth of water applied, feet Average area served per cu. foot per second, acres Yield per acre Year From- To- Period of submergence Whole season* in sacks averaging 100 pounds 1914 1915 1916 1917 Apr. 29 Apr. 21 Apr. 13 Apr. 11 Oct. 12 Oct. 1 Sept. 30 Sept. 21 4.65 4.87 4.27 4.37 68 66 70 62 56 51 56 51 60 45 39 39 Averag e 4.53 66 53 46 *Only days water used during pre-submergence period considered in computing whole season. Note.' — The amount of water used on this field was not measured in 1918 but it continued in crop and yielded, the fifth season, 36 sacks per acre. Such a record would not have been possible, however, without good preparation of the land in the first instance, careful use of water without waste, and keeping the field free from water grass. It is not only the annual depth of water required for rice that needs to be considered, because it is only after the rice fields have been brought to full submergence that the use is fairly uniform. In a measure, the "peak" needs during the initial flooding following seeding and during the period submergence is being brought to the required depth will govern the quantity that must be available, at times, to individual users as well as under entire systems. The figures in columns 9, 10, and 11 in table I and the figures in columns 5 and 6 in table III give some information on this question. These show a use during the submergence period ranging from 1 cubic foot per second for each 18 acres to 1 cubic foot per second to each. 74 acres irrigated. Columns 10 and 11 in table I show average use during the whole season from the beginning of the first irrigation through the submergence period; columns 5 and 6 in table III show use with the whole season considered only as including the entire submergence period and the days during the pre-submergence period water was actually used on the field. Fully satisfactory data for computing the demand of systems on the basis of acres served per cubic foot per second are not available, but the need seems to average 1 cubic foot per second to each 50 to 60 or more acres irrigated, with the prob- ability that the average area served per cubic foot per second will be Bulletin 325 RICE IRRIGATION MEASUREMENTS 55 increased for large systems as fields are left fallow, or cultivated to other crops to eliminate water grass. The demand of individual fields measured in acres served per cubic foot per second can be fairly well computed from the data at hand, and, for the pre-submergence period, from irrigation needs in general irrigation practice. Figures in columns 5 and 6 in table III are probably representative of needs on well handled fields where the soil is of the adobe or clay type most suitable for rice growing. These show an average use for the submergence period of about 66 acres per cubic foot per second and for the whole season of about 53 acres per cubic foot per second. More detailed data showing use by months are presented in table IV for eleven fields. The examples are not sufficiently alike in matter of practice, however, to warrant definite comparisons or exact conclusions, although they do indicate variation in individual use. Water requirements of rice during the initial flooding to start germination are, for individual fields, in excess of requirements during either the remainder of the pre-submergence period or during sub- Table IV Summary of Areas of Rice Land Served Per Cubic Foot of Water Per Second Owner or grower Year Area irri- gated, acres Soil Average area served per cubic foot per second, acres April May June July Aug. Sept. Evans Bros Hardin & Scheeline. B. E. Crouch. E. L. Adams.. Moulton Irrigated Lands Maupin & Emmons. Schell & Woodruff... E. L. Adams Mallon & Blevins. Spalding Co Hardin-Purcell-Locher 1916 1916 1916 1916 1917 1917 1917 1917 1918 1918 1918 187 133 302 39 823 115 172 71 5909 1880 150 Stockton clay adobe Tehama clay loam and clay Vina clay loam Stockton clay adobe Sacramento clay Willows clay Madera clay loam Stockton clay adobe Willows clay adobe Willows clay Willows clay adobe 83 36 14 27 40 21 12 45 55 36 14 95 90 27 27 50 25 71 45 55 27 19 54 83 27 20 33 29 71 37 53 28 53 50 55 29 27 42 33 71 41 62 31 67 59 59 24 24 43 42 83 40 71 55 83 55 77 25 56 UNIVERSIY OF CALIFORNIA EXPERIMENT STATION mergence. From 4 inches to 6 inches in depth is necessary to provide an adequate initial flooding, but not over 1 to 2y 2 inches in depth should be required in checks of normal size for subsequent pre-sub- mergence floodings. On this basis the "peak" pre-submergence duty per cubic foot per second, for individual fields, will vary from about 30 to 40 acres with a 6-inch flooding to from 40 to 60 acres, in both cases assuming that the initial flooding of the entire field is to be accomplished within seven to ten days, which about conforms to normal requirements. In practice a minimum irrigating head should be at least 2 cubic feet per second and a larger head is desirable, since general irrigation experience has taught that in flooding lands large rather than small heads give the most even and most economical irrigation. EVAPORATION The effect of evaporation on the duty of water in rice irrigations, already referred to as being greater than with other irrigated crops, is the factor over which least control is possible and probably none practicable. The well-known relation between evaporation and tem- perature suggests that within certain limits, the deeper the sub- mergence of rice fields the smaller the evaporation rate. For instance, water temperatures taken in submergence plots on the Norman experi- mental tract July 25, August 10, September 1, October 1, 1918, showed a wider daily variation in plots submerged 2 inches deep than in plots submerged either 4, 6, or 8 inches deep. This difference is generally most marked between 2-inch and 4-inch submergence, being 4 degrees on July 25, 8 degrees August 10, and only 1 degree on Sep- tember 1 and October 1. The full data for these dates taken from a continuous record extending from July 25 to October 1, 1918, are included in table V below. They indicate that as a practical matter any attempt through reducing the depth of submergence to save water by decreasing evaporation is not likely to be justified. Although it appears that evaporation must be accepted as largely an uncontrollable factor in rice irrigation, it is in a way a measurable factor. While the evaporation from a rice field is less than from a free water surface, owing to the shading by the rice plants, the loss from a free water surface gives a general indication of the loss from the latter. Seasonal records are available for the Norman experi- mental tract for 1918 and 1919 and for the Biggs Rice Field Station for 1917 to 1919. They indicate in a general way that during the four principal growing months, June to September, which roughly coincide with the submergence period, the evaporation loss reaches at least one-third of the water applied. Bulletin 325 RICE IRRIGATION MEASUREMENTS 57 Table V Variation in Water Temperatures in Submerged Rice Plots at Norman, 1918, With Different Depths of Submergence. Temperatures and Variation in Degrees Fahrenheit Depth Times of observation July 25 August 10 September 1 October 1 of submergence Water temper- ature Varia- tion Water temper- ature Varia- tion Water temper- ature Varia- tion Water temper- ature Varia- tion 2 inches 4 inches 6 inches 8 inches 8 a.m. 1 p.m. 6 p.m. 8 a.m. 1 p.m. 6 p.m. 8 a.m. 1 p.m. 6 p.m. 8 a.m. 1 p.m. 6 p.m. 73 96 87 72 91 88 73 90 88 72 90 88 23 19 17 18 66 90 83 68 84 84 70 85 87 70 85 86 24 16 17 16 74 89 87 75 88 89 76 86 88 77 85 87 15 14 12 10 66 75 76 66 74 75 65 73 76 65 73 76 10 9 11 11 Table VI Evaporation Record at Rice Experiment Field, Spalding Ranch, Norman, June 1 to September 30, 1918 and 1919 June July August September Total 4 mo. Year Period Inches Inches Inches Inches Inches Month 12.02 9.48 6.04 2.41 29.95 1918 Max. daily .49 .43 .27 .12 Min. daily .35 .26 .11 .07 Month 11.88 10.70 6.19 3.22 31.99 1919 Max. daily .38 .36 .22 .17 Min. daily .24 .21 .13 .06 Note. — Total evaporation June 1 to October 27, 1918, 32.30 inches; average per day .217 inch. Total evaporation May 26 to October 4, 1919, 34.42 inches; average per day, .252 inch. Evaporation pan 20 inches in diameter by 18 inches deep. 58 UNIVERSIY OF CALIFORNIA EXPERIMENT STATION Table VII Evaporation Record at Biggs Rice Field Station of Bureau of Plant Industry For Seasons of 1917, 1918, and 1919. Record Furnished by E. L. Adams and Jenkin W. Jones Year Period April May June July Aug. Sept. Oct. Total for period measur- ed Inches Inches Inches Inches Inches Inches Inches Inches 1917* 1918f 1919§ Month Max. daily Min. daily Month Max. daily Min. daily Month Max daily Min. daily 4.09 .34 .07 6.11 .39 .08 8. lit .57 .32 9.45 .57 .19 12.22 .69 .15 8.99 .43 .15 10.11 .41 .22 8.68 .47 .16 9.69 .41 .18 8.18 .42 .16 7.03 .42 .06 7.86 .38 .15 6.16 .31 .06 3.81 .26 .03 5.50 .32 .47 4.48 .40 .02 4.25 .20 .02 44.10 44.33 36.29 *Record covers April 1 to September 30 (28 days in April). fRecord covers May 13 to October 31 (29 days in Oct.). + Record covers one-half month. §Record covers June 1 to October 31. Note. — Evaporation pan 72 inches in diameter by 24 inches deep. EXPERIMENTS AT BIGGS AND NORMAN Because rice is a relatively new crop in California growers have been compelled to feel their way in the matter of irrigation on the basis of such knowledge as has been brought from the South and from foreign countries, and such experience as has been gained and such study as has been possible since rice growing commenced on a com- mercial scale in California about 1912. The state also has been com- pelled, in acting on permits to appropriate water for the irrigation of rice, to reserve final judgment as to the water needs of this crop until more information might be available. Aside from the matter of the proper duty of water in the irrigation of this crop, it has been important that the proper time and methods of applying the water be known. The experiments at Biggs and at Norman, already referred to, have made some progress in supplying this fundamental information and have suggested further experiments it is important to undertake. Bulletin 325 RICE irrigation MEASUREMENTS 59 As outlined in the previous publication of this station on rice irrigation,* the purpose of the experiments at Biggs, later duplicated for two years at Norman, has been to determine the effect of varying the dates of submergence of the crop, of varying the depths of sub- mergence, of not giving continuous submergence during the usual submergence period, of slowly changing versus stagnant water, and of fluctuating the depth of submergence. The tests at Biggs were made on one-fifth acre plots during 1914, 1915, 1916, 1918 and 1919, and on one-tenth acre plots during 1917, in which year the original tract was fallowed. The tests at Norman in 1918 and 1919 were made with one-fourth acre plots. The soil on which the Biggs experiments were conducted is the black clay adobe (Stockton clay adobe) typical of most of the land utilized for rice growing around Gridley, Biggs, Richvale and Nelson. The soil at Norman on which the experiments were duplicated in 1918 and 1919 is classified as Willows clay and locally known as "goose land." Reporting on the alkali content of the Norman soils, Dr. C. B. Lipman, of the Division of Soil Chemistry and Bacteriology of the College of Agriculture, describes them as representing a silty clay loam surface soil with a slightly heavier subsoil, and with their physical condition rather poor. The variation in alkali content (in this case largely in the form of sodium chloride and sodium sulfate, with traces of gypsum and sodium carbonate, or "black alkali") ranged in the analyses made by Dr. Lipman from too little to warrant analysis to 1.15 per cent ; and observations in the field during the growing season indicated an even stronger alkali content in patches than the samples analyzed showed. Ground water stood about 3 feet below the surface at the beginning of the season in 1918 and had raised about 6 inches by the end of that season; during 1919 the fluctuation was between 2.5 and 3.5 feet, the greater depth occurring in July and August. Because of the great variation in the soil at the Norman station, the plots were arranged in quadruplicate, while they were duplicated (excepting in 1917) at Biggs. The location of the Biggs experiments was on the Biggs Rice Field Station of the Bureau of Plant Industry and at Norman at the northern end of the Spalding Ranch about five miles south of "Willows. The results of the experiments at both Biggs and Norman are grouped in tables VIII, IX, and X below. * Univ. of Calif. Coll. of Agr., Exp. Sta. Bull. 279. 60 UNIVERSIY OF CALIFORNIA EXPERIMENT STATION Table VIII Results of Experiments at Biggs and Norman on the Effect on Yields of Varying the Date of Submergence of Rice Fields After Emergence of the Plants Above the Ground. Depth of Submergence 6 Inches. Location Yields of rice in pounds per acre with different dates of beginning submergence Year 15 days after emergence 30 days after emergence 45 days after emergence 60 days after emergence 1914 1915 1916 1917 1918 1919 1918 1919 Biggs do do do do do Norman do 4510 3860 3750 4220 3420 1700 3568 2682 5610 4270 4020 4500 4185 2230 3108 2809 5410 4100 3890 4310 3240 2050 2604 2096 5240 3910 3610 4040 4115 1980 1933 1650 Average for 3 Average for 3 3iggs 3577 3125 4136 2958 3833 2350 3816 Gorman 1791 Table IX Results of Experiments at Biggs and Norman on the Effect on Yields of Varying the Depth of Submergence of Rice Fields. Submer- gence Begun 30 Days After Emergence. Location Yields of rice in pounds per acre with different depth s of submergence Year 2 inches 4 inches 6 inches 8 inches 1914 Biggs 5010 5490 5670 5220 1915 do 4030 4290 4510 4400 1916 do 3620 3760 3900 3940 1917 do 4260 4440 4520 4480 1918 do 4635 4215 4035 4015 1919 do 3000 2990 3050 2710 1918 Norman 2722 3154 3425 3132 1919 do 2452 2275 2747 1876 Average for BiVcs 4092 4197 4281 4127 Average for I s Gorman 2587 2715 3086 2504 Bulletin 325 RICE IRRIGATION MEASUREMENTS 61 Table X Results of Experiments at Biggs and Norman on the Effect on Yields of Slowly Changing Water, Stagnant Water, No Submergence, and Fluctuation of Depth During Submergence. Sub- mergence Begun 30 Days After Emergence Location Yields of rice in pounds per acre with different water treatments Year Slowly changing water; 6-inch submergence Stagnant water; 6- inch sub- mergence No submergence but soil kept moist Fluctuation of depth of sub- mergence 1914 Biggs 4790 4940 2440 5290 1915 do 4210 3990 2480 4160 1916 do 3460 3800 2100 3690 1917 do 4230 4405 2490 4360 1918 do 3615 2550 2860 3625 1919 do 3000 2600 1250 2950 1918 Norman 2670 2504 1800 3187 1919 do 2212 1239 2265 2909 Average for Bis-ers 3884 3714 2270 4012 Average for I Gorman 2441 1871 2033 3048 Time of submergence. — The figures for Biggs in table VIII con- sistently showed the largest yields from beginning submergence of the rice land 30 days after emergence of the crop above the ground; and that with the single exception of 1918, beginning submergence 45 days after emergence was better than either 15 or 60 days after emergence. The advantage gained by beginning submergence 30 days after emergence averaged 15 per cent, or 5% sacks, over 15-day sub- mergence, but only about 8 per cent, or about 3 sacks, over 45-day and 60-day submergence. At Norman, however, the average results seem to indicate that the beginning of submergence on such soils as Willows clay, with which alkali is largely associated, can best be placed nearer to 15 days after emergence than 30 days after. For 1919, it is to be noted, the larger yield at Norman resulted from begin- ning submergence 30 days after emergence, as at Biggs; and by segregating the 1919 records according to whether the soil should be classified as "alkali" or "good," the tendency for the 30-day sub- mergence to give the better results is increased. Nevertheless, the average in favor of the earlier submergence on alkali lands is not overcome by the 1919 results at Norman, and this is not changed even by making a similar segregation for 1918. Apparently the ruling 62 UNIVERSIY OF CALIFORNIA EXPERIMENT STATION condition is the alkali, and that early submergence of the alkali lands, by earlier reducing the alkali concentrations in the surface soils, gives a protection to the young plants that is not needed where the alkali is not present. In further analysis of the results presented in the above table it should be noted that the largest advantage of 30-day over 15-day submergence occurred in 1914, when the land was first seeded to rice. While this is a suggestion that the advantage of one treatment over Moist soil Submergence Submergence Submergence Submergence Fluctuating without 2 inches 4 inches 6 inches 8 inches depth of ? submergence deep deep deep deep submergence Fig. 2. — Typical stool of rice from experimental plots at Norman, 1919. These show relative growth under different depths of submergence. another is likely to be greatest on new land, one experiment is not conclusive. Probably the most important factor to determine practice will be the advantage of early over late submergence as compared to the extra cost of the early submergence. Since the time of ripen- ing of the crop apparently is not greatly affected by the time sub- mergence commences* the cost advantage of the 15-day or 30-day submergence over the 45-day or 60-day submergence, where alkali is not a factor requiring the early submergence, is not yet demon- strated. * For instance, in 1918, which is typical, the plots submerged 15 days after emergence matured their crop only 4 days in advance of the plots receiving 30-day, 45-day, and 60-day submergence. Bulletin 325 RICE IRRIGATION MEASUREMENTS 63 Depth of submergence. — With two exceptions at Biggs — 1916 and 1918 — the experiments with depth of submergence summarized in table IX gave the best yields with a submergence of 6 inches through- out the submergence period. But the increased crop over the next highest plots obtained with a 6-inch submergence ranged from less than 1 to only 4 per cent, averaging for the six years about 2 per cent. For the two years at Norman the 6-inch submergence also produced best, with an average increase of 13 per cent above the 4-inch sub- 30 days lOO days 120 days after beginning after beginning after beginning submergence. submergence. submergence. Fig. 3. — Kepresentative rice plants at different submergence. stages of development during mergence. Expressed in sacks of rice per acre, the average advantage of the 6-inch submergence over the 4-inch submergence was .84 of a sack at Biggs and 3.71 sacks at Norman. The average increase for the first two years at Biggs, which is a better figure with which to compare the 2-year average at Norman, was only 2 sacks per acre. While these experiments seem to indicate that it is good practice to submerge to a depth of 6 inches, the small increases at Biggs raise the question as to whether the increased cost of 6-inch over a 4-inch submergence is justified by the return. This increased cost should be figured both in money for extra water and extra labor to maintain the deeper submergence, and also in the extra water which the state permits the irrigator to withdraw from the stream. The 13 per cent increase at Norman probably justifies the 6-inch submergence, the 64 UNIVERSIY OF CALIFORNIA EXPERIMENT STATION 2 per cent increase at Biggs probably does not. A more complete determination of this must wait on further intensive experiments. Certainly even a 2-inch submergence made a more creditable showing than might have been expected. In 1918 the 2-inch submergence gave by far the best yield at Biggs, in 1919 it gave next to a 6-inch sub- mergence at Norman; and in no year, either at Biggs or at Norman, did it fail to give within 12 per cent of the maximum for that year, averaging but 4 per cent below the average maximum at Biggs — equivalent to 1.79 sacks per acre — and 16 per cent below the maximum at Norman — equivalent to 5 sacks per acre. Stagnant versus changing water. — The normal condition in the rice checks is for water during submergence to be slowly changing within an indefinite area between the inlet of the water and the gate or gates leading to the next lower check, but with a considerable por- tion of each check stagnant or nearly so. The relative yields under slowly changing and stagnant water given in the third and fourth columns in table X do not show any constant advantage, excepting in the case of the Norman experiments. The Biggs results show the greater yields in one-half of the six years under observation to fall under each treatment, but with a 4% per cent average advantage, equivalent to 1.70 sacks per acre, with the slowly changing water. At Norman the slowly changing water gave definitely better results each year, with probably an abnormal advantage in 1919. The 2-year period at Norman is of course too short for definite conclusion, but the presence of alkali in considerable quantities there, taken with the appearance of the plants in the stagnant and slowly changing plots, indicates that on alkali soil stagnant water during submergence is most likely to be injurious, depending on the amount and kind of alkali present. Here again further studies are necessary for a final determination of the matter. Fields moist but with no submergence. — Column 5 in table X seems definitely to make clear that under such conditions as are present on the Stockton clay adobe at Biggs, merely keeping the rice fields moist instead of flooded during the usual submergence period will not give fully satisfactory yields. It is to be noted, however, that excepting in 1919, the yields under the "moist" treatment were considerable, both at Biggs and at Norman. Apparently California conditions may permit of some commercial yields without submergence, although to what extent this will prove profitable does not appear. However, the results of the "moist" treatments were not always satisfactory from the standpoint of the quality of the rice. Bulletin 325 RICE irrigation MEASUREMENTS 65 Fluctuation of depth of submergence. — The plan of fluctuating submergence followed in these experiments was to hold a uniform depth of 4 inches to 6 inches after beginning submergence until ' ' boot- ing" was noticeable, then to lower the depth to 1% to 2 inches until the first heads appeared, finally bringing it back to a depth of 4 to 6 inches until the rice was ready for draining. This plan of fluctuating depth was, however, somewhat altered in 1918. As compared with the other results listed in table X, fluctuating the depth gave the better yields. As compared with the yields with continuous 4-inch or 6-inch submergence throughout the submergence period as listed in table IX, however, the yields with fluctuating depths were definitely below the best at Biggs, although in less measure at Norman. Apparently some fluctuation, as frequently results from interruption of water source, is not markedly injurious ; and it may be possible that further experiments will show conditions under which fluctuation of depth will be advantageous, especially if California rice fields come to have insect troubles similar to those experienced in the Southern rice fields.* RICE GROWING AND ALKALI INJURY The well-known injury that results to lands from rise of ground water, with attendant damage from alkali, will in time automatically reduce the area that can profitably be devoted to rice growing unless both preventive and corrective measures of radical nature are taken. This injury may be both to the lands planted to rice and to neigh- boring lands in which the ground water is brought up through the large amount of water applied in rice growing. The most important preventive measure is to restrict rice growing to soils that do not require over, say, 5 acre-feet of water per acre per annum, such as the clay and clay adobes of the Willows, Capay, Yolo, Stockton, and Sacramento series already referred to as being, so far as observations have gone, the most satisfactory soils, from a water standpoint, for rice growing. It can not be too emphatically stated that the continued growing of rice on loam soils not underlain by an impervious stratum that prevents deep percolation of water will result in very great damage. Fortunately, the higher cost of irrigating loam soils devoted to rice will, as the price of rice again becomes normal, tend to eliminate such soils for this crop. Nevertheless, the important corrective meas- ure required — thorough drainage — should not be delayed; for unless this is provided, much injury will result from only a few years of *U. S. Dept. of Agr., Farmers' Bull. 1086. 66 UNIVERSIY OF CALIFORNIA EXPERIMENT STATION growing rice on such land — such injury as already has occurred or become imminent in numerous Sacramento Valley rice-growing sec- tions. Thorough drainage is also of course important in the rice areas of the heavier soils, not only to keep these soils good for rice and to make the rotation of crops necessary for water grass eradication possible, but also to prevent damage to other lands. It is already plain that the drainage needed is much more than that incident to removing and caring for the water on the rice fields at the close of the season when submergence is stopped. Concerted neighborhood action, and not merely individual provision for drainage, will be required in carrying out both preventive and corrective measures adequate to meet the menace. IRRIGATION AND WATER GRASS No study of rice irrigation can overlook the great damage done to rice fields by water grass. At present, outside of irrigation and drainage, this pest is the controlling factor in the permanence of the rice industry in California. It seldom does great damage in the first year on new or adequately fallowed land, but with a normal price for rice three years is practically the limit of profitable rice growing until the fields are again cleared. From an irrigation stand- point, the most important preventive measure to meet the situation is to keep the banks of irrigation ditches, principally the main and field laterals, entirely clean of water grass either by pulling or cutting out the water grass, or by pasturing sheep on the ditch banks before the seed has formed. Keeping drains and sloughs free of both water grass and tules is also absolutely necessary if the danger is to be minimized. Thus far no satisfactory mechanical device for removing water grass seed from the water in the ditches has been devised. SUMMARY In 43 full-season measurements of the amount of water used in rice irrigation in Sacramento Valley, 1914 to 1918, the total depth of water applied ranged from 3.91 to 18.70 feet, and the net depth, after deducting measured or estimated waste, ranged from 3.91 to 13.43 feet. In 32 full-season observations on clay and clay adobes of the Willows, Sacramento, Stockton, and Capay series the total depth of water applied ranged from 3.91 to 10.09 feet, the net depth from 3.91 to 9.11 feet, and the average depth from 3.94 to 5.72 feet. The average net depth of water applied to 22,404 acres embraced in the 43 full-season observations mentioned was 4.89 feet. Of this Bulletin 325 RICE IRRIGATION MEASUREMENTS 67 area 21,419 acres was clay or clay adobe of the Willows, Sacramento, Stockton, or Capay series. A four-year record of use on 39.5 acres of Stockton clay adobe near Biggs, well prepared and well irrigated, showed a range in depth of water applied of 4.27 to 4.87 feet and an average of 4.53 feet. An annual depth of 5 feet of irrigation water for rice is sufficient for the principal rice soils of Sacramento Valley, viz : for the clays and clay adobes of the Willows, Stockton, Sacramento, Capay and Fig. 4. — A Sacramento Valley rice field showing drooping of heads at the ripening period when irrigation water is drawn off. Yolo series. Pervious loam soils require an excessive amount of irrigation water, and from a water standpoint are not suitable for rice growing. The use on individual fields of 1 cubic foot per second of irriga- tion water to 30 to 40 acres during the first flooding after seeding is not excessive. Owing to the fact that all growers are not ready for the first flooding at the same time, canal diversions at this rate are not necessary, although probably as much as 1 cubic foot per second to about each 50 acres served is desirable during the period of initial flooding. The seasonal use averages about 65 acres per cubic foot per second. 68 UNIVERSIY OF CALIFORNIA EXPERIMENT STATION About one-third of the water applied to rice fields is lost by evapo- ration from the surface of the standing water during submergence. This factor in the duty of water cannot be controlled. A 6-year series of experiments at Biggs, duplicated for 2 years near Norman, generally show maximum rice yields from submerging rice fields 6 inches deep beginning 30 days after emergence of the plants above ground. An exception to this was found on the alkali soils in the Norman plots, from which the best yields were obtained from submergence beginning 15 days after emergence. The advantage from submerging rice fields 6 inches deep beginning 30 days after emergence on all but alkali land, when compared with the results from submerging to a less or greater depth or beginning submergence earlier or later after emergence of the plants, may not average sufficient to offset the difference in cost of irrigation by the different methods. Constant movement of irrigation water through the rice checks during the period of submergence is necessary only where the soil contains alkali in sufficient quantities to affect the plants. Keeping rice fields only moist or "muddy" throughout the grow- ing season gives reduced yields of poor quality. Fluctuating depth of submergence may prove beneficial in rice irrigation, but experiments to date have, not fullly demonstrated this for California conditions. It is imperative that ground water and rise of alkali be controlled in California rice fields both by confining rice growing to the heavier, impervious clays and clay adobes, and by thorough and adequate drainage facilities embracing the entire areas affected or likely to be affected. A prime factor in control of water grass in rice fields is the keeping of banks of canals and ditches, principally lateral and field ditches, entirely free of this pest by pulling, cutting or pasturing before the seed is formed. An almost equally important factor is the keeping of drains and sloughs free of both water grass and tules. Bulletin 325 RICE IRRIGATION MEASUREMENTS 69 Appendix Summary of Gross Duty of Water Measurements on Rice Supplied From Operation Records of Sacramento Valley Irrigation Companies and Individual Growers (Areas as Reported by Growers). Company or grower County Year Total area for which water diverted or supplied Soil classification Average quantity of water div- erted per acre irrigated Acres Acre-feet Yolo Water & Power Co. Yolo 1915 300 Willows clay adobe 6.38 do do 1916 7,517 Willows clay adobe and Capay clay 6.31 do do 1917 12,662 do 5.35 do do 1918 10,000* do 4.64 do do 1919 6,141 do 7.75 Butte Farm Land Co Butte 1919 1,370 Stockton clay adobe 4.00 E. B. Copeland do 1919 830 do 4.61 B. E. Crouch do 1919 2,085 Clay loam and adobe 7.53f Cbico Rice Land Co do 1919 1,236 Stockton clay adobe 5.12 Clara Cramer do 1919 1,391 260 do 5.77 G. B. Randall do 1919 do 5.33 W. G. Davis do do do 1919 1919 1919 622 370 1,348 do do Stockton and Willows 7. 33 J Meikle Bros 4.61 Pacific Farms Co 5.31 clay adobe Union Ent. Co do 1919 922 Stockton clay adobe do 5.77 Western Rice Growers.... do 1919 1,578 4.38 C. W. Kesterson do 1919 196 do 7.24§ D. A. Sheelove 1919 300 10.73 Parrott-Phelan 1919 3,160 9.81 A. N. Lewis Est 1919 400 10.80 Sutter Basin Co 1919 7,400 7.50 Western Rice Growers.... Glenn 1919 195 Willows clay 5.67 do do 1919 90 Willows clay adobe 7.28 Samuels Bros do 1919 198 do 4.49 Willard & Garnett do 1919 320 do 5.91 Rasmussen do do 1919 1919 458 300 do Willows clay 4.76 Tyson 6.56 Freed do 1919 109 Willows clay adobe 7.66 Willows Rice Co do 1919 700 do 6.71 Spalding Ranch do 1919 2,814 Willows clay 5.79 *Area not all harvested. fLands badly cut up by sloughs; land more or less lighter than adobe. t- ^Excessive waste on this farm. STATION PUBLICATIONS AVAILABLE FOR FREE DISTRIBUTION BULLETINS No. 168. 169. 185. 208. 250. 251. 252. 253. 257. 261. 262. 263. 266. 267. 268. 270. 271. 272. 273. 274. 275. 276. 277. 278. 279. 280. 282. 283. No. Observations on Some Vine Diseases in 285. Sonoma County. 286. Tolerance of the Sugar Beet for Alkali. 288. Report of Progress in Cereal Investiga- tions. 290. The Late Blight of Celery. The Loquat. 297. Utilization of the Nitrogen and Organic 298. Matter in Septic and ImhofT Tank 299. Sludges. 300. Deterioration of Lumber. 301. Irrigation and Soil Conditions in the Sierra Nevada Foothills, California. 302. New Dosage Tables. Melaxuma of the Walnut, " Juglans regia." 303. Citrus Diseases of Florida and Cuba 304. Compared with Those of California. Size Grades for Ripe Olives. 308. A Spotting of Citrus Fruits Due to the Action of Oil Liberated from the Rind. Experiments with Stocks for Citrus. 309. Growing and Grafting Olive Seedlings. A Comparison of Annual Cropping, Bi- 310. ennial Cropping, and Green Manures 311. on the Yield of Wheat. 312. Feeding Dairy Calves in California. 313. Commercial Fertilizers. 314. Preliminary Report on Kearney Vine- 316. yard Experimental Drain. 317. The Common Honey Bee as an Agent in 318. Prune Polination. 319. The Cultivation of Belladonna in Cali- 320. fornia. 321. The Pomegranate. 322. Sudan Grass. 323. Grain Sorghums. Irrigation of Rice in California. 324. Irrigation of Alfalfa in the Sacramento Valley. 325. Trials with California Silage Crops for Dairy Cows. The Olive Insects of California. The Milch Goat in California. Commercial Fertilizers. Potash from Tule and the Fertilizer Value of Certain Marsh Plants. The June Drop of Washington Navel Oranges. The Almond in California. Seedless Raisin Grapes. The Use of Lumber on California Farms. Commercial Fertilizers. California State Dairy Cow Competition, 1916-18. Control of Ground Squirrels by the Fumigation Method. Grape Syrup. A Study on the Effects of Freezes on Citrus in California. I. Fumigation with Liquid Hydrocianic Acid. II. Physical and Chemical Pro- perties of Liquid Hydrocianic Acid. I. The Carob in California. II. Nutri- tive Value of the Carob Bean. Plum Pollination. Investigations with Milking Machines. Mariout Barley. Pruning Yound Deciduous Fruit Trees. Cow-Testing Associations in California. The Kaki or Oriental Persimmon. Selections of Stocks in Citrus Propagation. The Effects of Alkali on Citrus Trees. Caprifigs and Caprification. Control of the Coyote in California. Commercial Production of Grape Syrup. The Evaporation of Grapes. Heavy vs. Light Grain Feeding for Dairy Cows. Storage of Perishable Fruit at Freezing Temperatures. Rice Irrigation Measurements and Ex- periments in Sacramento Valley, 1914- 1919. No. 65. The California Insecticide Law. 70. Observations on the Status of Corn Growing in California. 76. Hot Room Callusing. 82. The Common Ground Squirrels of California. 87. Alfalfa. 109. Community or Local Extension Work by the High School Agricultural Depart- ment. 111. The use of Lime and Gypsum on California Soils. 113. Correspondence Courses in Agriculture. 114. Increasing the Duty of Water. 115. Grafting Vinifera Vineyards. 117. The Selection and Cost of a Small Pump- ing Plant. 124. Alfalfa Silage for Fattening Steers. 126. Spraying for the Grape Leaf Hopper. 127. House Fumigation. 128. Insecticide Formulas. 129. The Control of Citrus Insects. 130. Cabbage Growing in California. 131. Spraying for Control of Walnut Aphis. 133. County Farm Adviser. 135. Official Tests of Dairy Cows. 136. Melilotus Indica. 137. Wood Decay in Orchard Trees. 138. The Silo in California Agriculture. 139. The Generation of Hydrocyanic Acid Gas in Fumigation by Portable Machines. CIRCULARS No. 140. 143. 144. 147. 148. 152. 153. 154. 155. 156. 157. 158. 159. 160. 164. 165. 167. 168. 170. 172. 173. The Practical Application of Improved Methods of Fermentation in California Wineries during 1913 and 1914. Control of Grasshoppers in Imperial Valley. Oidium or Powdery Mildew of the Vine. Tomato Growing in California. "Lungworms". Some Observations on the Bulk Handling of Grain in California. Announcement of the California State Dairy Cow Competition, 1916-18. Irrigation Practice in Growing Small Fruits in California. Bovine Tuberculosis. How to Operate an Incubator. Control of the Pear Scab. Home and Farm Canning. Agriculture in the Imperial Valley. Lettuce Growing in California. Small Fruit Culture in California. Fundamentals of Sugar Beet Culture under California Conditions. Feeding Stuffs of Minor Importance. Spraying for the Control of Wild Morning- Glory within the Fog Belt. The 1918 Grain Crop. Fertilizing California Soils for the 1918 Crop. Wheat Culture. The Construction of the Wood-Hoop Silo. CIRCULARS — Continued No. 174. Farm Drainage Methods. 175. Progress Report on the Marketing and Distribution of Milk. 176. Hog Cholera Prevention and the Serum Treatment. 177. Grain Sorghums. 178. The Packing of Apples in California. 179. Factors of Importance in Producing Milk of Low Bacterial Count. 181. Control of the California Ground Squirrel. 182. Extending the Area of Irrigated Wheat in California for 1918. 183. Infectious Abortion in Cows. 184. A Flock of Sheep on the Farm. 185. Beekeeping for the Fruit-grower and Small Rancher or Amateur. 187. Utilizing the Sorghums. 188. Lambing Sheds. 189. Winter Forage Crops. 190. Agriculture Clubs in California. 191. Pruning the Seedless Grapes. 193. A Study of Farm Labor in California. 195. Revised Compatibility Chart of Insecti- cides and Fungicides. 197. Suggestions for Increasing Egg Produc- tion in a Time of High-Feed Prices. No. 198. Syrup from Sweet Sorghum. 201. Helpful Hints to Hog Raisers. 202. County Organization for Rural Fire Control. 203. Peat as a Manure Substitute. 204. Handbook of Plant Diseases and Pest Control. 205. Blackleg. 206. Jack Cheese. 207. Neufchatel Cheese. 208. Summary of the Annual Reports of the Farm Advisors of California. 210. Suggestions to the Settler in California. 213. Evaporators for Prune Drying. 214. Seed Treatment for the Prevention of Cereal Smuts. 215. Feeding Dairy Cows in California. 216. Winter Injury or Die-Back of the Walnut. 217. Methods for Marketing Vegetables in California. 218. Advanced Registry Testing of Dairy Cows. 219. The Present Status of Alkali. 220. Unfermented Fruit Juices. 221. How California is Helping People Own Farms and Rural Homes.