﻿8 BULLETIN 10, U. S. DEPARTMENT OF AGRICULTURE. 



The results, although not absolutely conclusive, point to the fol- 

 lowing facts: 



(1) In the open, well-drained soil, typical of that found in the 

 floor of the Sacramento Valley, the general tendency is toward an 

 increase in yield of alfalfa with the increased amounts of water ap- 

 plied up to at least 48 inches. 



(2) There is a limit beyond which the increase in yield will not 

 pay for increased cost of applying the water, and for such conditions 

 as are found on the University farm this limit is in the neighborhood 

 of 30 inches applied as a total for the season. 





UNIRRIGATED 



FOUR 7 '/2 IN. IRRIGATIONS 





CROP 



CROP 





1ST 



2ND 



3RD 



4.TH 



5TH 



6th 



1ST. 



2nd 



3RD 



4th 



5th 



6th 



1.8 

 1.7 

 1.6 

 1.5 



£1.4 



V 3 



a 12 



w I.I 

 a 



en 1-0 

 |9 



h 8 



z 



- .7 



Q 



-J .6 



Id 



> * 



.4 

 .3 

 .2 



.1 

 













• 



































































































- 

































































































































































































































































































































































































































































































































































































































































Fig. 3. — Comparative yield of unirrigated and irrigated alfalfa, by crops. 



In applying these conclusions to other localities, it is well to re- 

 member that local conditions are always the controlling factors. 

 The character and condition of the soil, the climate, the rainfall, the 

 length of the growing season, and the age of the alfalfa, all have 

 their effect upon the yield, and each general locality will show differ- 

 ent results and a different economic duty of water. 



WHEN TO IRRIGATE ALFALFA. 



In order to determine if possible at what stage of growth after 

 cutting the water should be applied to produce the best results, checks 

 17 to 28, inclusive, were divided into three groups of four checks 

 each, and during 1910 and 1911 they were treated in the following 

 manner : 



