BULLETIN 
S. DEPABTMEXT 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 
4th 
5TH 
6th 
1ST 
2ND 3RD 
4th '5th 
6th 
1.8 
1.7 
1.6 
1.5 
LJ..4 
1.3 
hJ 1 I 
a " 
in •' 
§9 
^ 8 
- .7 
Q 
-J .6 
UJ 
> 5 
A 
3 
.2 
.1 
.0 
Fig. 3. — Comparative yield of unirngated 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 dutv 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 thev were treated in the following 
manner 
