97 



Yield in tons per acre. 



Depth 



of water applied. 



In 1910. 



In 1911. 



None. 



12 



24. . . . 



30 



32 



36 



48 



4.08 

 4.79 

 6.43 

 8.09 



7.60 



8.45 



6.03 

 7.52 

 8.38 

 9.50 

 9.20 

 9.33 

 9.65 



The plants were two years old in 1910 and three years old in 1911. The 

 rainfall during the fall, winter and spring preceding the summer of 1910 

 was about 12 inches, and preceding the summer of 1911 it was about 22 

 inches. The rainfall during the growing season from the beginning c 

 April to the end of October in both years was less than 1 inch. The soil 

 was a andy loam of great depth and the substantial yields obtained with- 

 out irrigation show the power of this soil to retain the moisture produced 

 by the winter and spring rains. The results show that the yield increases 

 materially with an increase in the amount of water applied up to 30 inches, 

 which gave a greater yield than 32 or 36 inches and almost as great as 

 48 inches. 



The experiments made in Montana, Idaho and California, described 

 above seem to indicate that 30 inches of water carefully applied will give 

 .almost maximum yields. While greater yields may be otbained-by adding 

 greater quantities of water, the increase is only small and will in most 

 cases not pay for the extra water. Where water is valuable it may be more 

 economical to use even less than 30 inches. The best practice in southern 

 California where water is valuable compares closely with the experiments 

 mentioned. At Pomona, California, the rainfall for 1903-4 was about i 

 inches; the quantity of water applied by pumping averaged 2.3 feet in 

 -depth and the yield of cured hay averaged 1 to 1.5 tons per acre per c 

 ting, five or six cuttings being common. 

 3. Number of Irrigations. 



Where there is sufficient moisture in the soil due to rainfall no irri- 

 gation may be necessary for the first crop. For each succeeding crop i 

 is common practice to apply one irrigation either before or after cutting. 

 On gravelly porous soil and on shallow soils, two or even three irrigations 

 for each crop may be preferable. Irrigation before cutting is the custom 

 in the Yellowstone Valley of Montana. It has the advantage that the soil 

 being shaded by the plant, the evaporation of soil water is decreased II 

 :also tends to prevent baking of the soil and permits an earlier irrigation 

 for the last crop, which is an advantage if the available water runs short 

 before the end of the season. The disadvantages of irrigating before 

 cutting are that the plants interfere more or less with the distribution of 

 water and that the soil may take considerable time to dry out sufficient y 

 to permit harvesting. For these reasons many irrigators prefer t 

 .after each cutting. 

 4 The Proper Time to Irrigate Alfalfa. 



' Farmers' Bulletin No. 373 on Irrigation of Alfalfa written by S.muc 

 Fortier of the U. S. Department of Agriculture, gives the follow,! 

 information on the proper time to irrigate alfalfa, winter Irngation. wmter 

 killing and seeding of alfalfa: 



