346 DRY-FARMING 
EFFECT oF VARYING IRRIGATIONS ON CROP YIELDS PER 
ACRE 
DeptH OF 
WATER WHEAT Corn ALFALFA | PoTATOES 
AppLiep | (Bushels) | (Bushels) | (Pounds) (Bushels) (Tons) 
(INcHES) 
5.0 40 — — 194 25 
7.5 41 65 — —_ _ 
10.0 41 80 = 213 26 
15.0 46 78 = 253 27 
25.0 49 77 10,056 258 ae 
35.0 55 _ 9,142 291 26 
50.0 60 84 | 13,061 — = 
The soil was a typical arid soil of great depth and 
had been so cultivated as to contain a large quantity 
of the natural precipitation. The first five inches 
of water added to the precipitation already stored 
in the soil produced forty bushels of wheat. Dou- 
bling this amount of irrigation water produced only 
forty-one bushels of wheat. Even with an irrigation 
of fifty inches, or ten times that which produced forty 
bushels, only sixty bushels of wheat, or an increase 
of one half, were produced. A similar variation 
may be observed in the case of the other crops. The 
first lesson to be drawn from this important principle 
of irrigation is that if the soil be so treated as to 
contain at planting time the largest proportion of 
the natural precipitation, — that is, if the ordinary 
methods of dry-farming be employed, —crops will be 
