WATER REQUIREMENT OF CROPS UNDER FIELD CONDITIONS. 85 
Table LXXIII. — Effect of different amounts of irrigation water on the water requirement 
of crops under field conditions, according to Widtsoe (1912, pp. 55-57). 
Water requirement, including evaporation, for— 
Water applied. 
Wheat. 
Oats. 
Barley. 
Corn. 
Alfalfa. 
Sugar 
beets. 
Carrots. 
Pota- 
toes. 
Cab- 
bage. 
Onions. 
Irrigation water add- 
ed, in acre-inches: 
3 75 
423 
557 
856 
869 
94S 
596 
— - — - 
569 
1,136 
1,136 
1,255 

513 
276 
275 
10 
621 
571 
12.5 
2,214 
"3," 12S" 
4,248 
15 
20 
25 
30 
1,038 
""i,"3i7* 
845 
897 
695 
""998' 
356 
416 
474 
527 
977 
946 
1,052 
1,253 
663 
682 
"'889' 
572 
""760" 
""880" 
1.411 
1,466 
"*2,242" 
2. 170 
_ _• 
"2,485 
35 
1,530 
39.5 
1,263 
:::::::: 
40 .. 
5,058 
45 
"i,"s69" 
1,566 
3,060 
50 
1,480 
1,186 
1,087 
60 . 

1,071 
3,292 
65 .. 
70... 
7,419 
5.54 
Soil water and rain- 
fall used by crop 
in addition to irri- 
gation: 
Inches 
13. 74 
9.66 
9.66 
5.54 
14.91 
10.25 
10.25 
6.17 
5.54 
Widtsoe's results show clearly the great increase in the water 
requirement, which includes the evaporation as well, when the 
quantity of irrigation water applied is increased, the largest amounts 
of water applied resulting in a water requirement of about three times 
that observed when small quantities of irrigation water were used. 
CROPS GROWN WITHOUT IRRIGATION. 
LEATHER S EXPERIMENTS. 
Leather (1911) also measured the water requirements of a number 
of crops under field conditions. The land selected for the purpose 
was kept fallow during the rainy (monsoon) season, and the crops 
were sown at the beginning of the dry season. Moisture determina- 
tions were made in each plat soon after the plants were above ground 
and again at harvest. The difference in the amount of water in the 
soil at the time of these two measurements plus the water added 
through rainfall represented the total loss of water. The rainfall 
during the experimental period was very low, being only 0.4 inch at 
Pusa in 1908-9 and 0.2 inch in 1909-10, making the conditions excep- 
tionally favorable for an experiment of this kind. Moisture deter- 
minations at seeding time and at harvest were also made hi a part of 
the field which was kept fallow throughout the experiment. The 
difference in these determinations gave the loss due to evaporation 
from the fallow plat. The evaporation loss from the cropped plats 
was assumed to be the same as from the fallow plat. The difference 
between the total amount of water lost and that lost through evapora- 
285 
