78 
Table LXIX. 
WATER REQUIREMENT OF PLANTS. 
Water requirement of crop plants at Gottingen, Germany, according to 
Von Seelhorst (1906, 1908, and 1908a)— Continued. 
Relative Water Requirement Compared with Rye. 
Crop. 
First 
series. 
Second 
series. 
Third 
series. 
Fourth 
series. 
Rye 
100 
100 
95 
100 
112 
100 
Barley 
77 
Potatoes 
72 
89 
77 
Wheat 
Beets 
87 

' 1 
According to the above figures, rye and barley have about the same 
water requirement. Potatoes have a water requirement three-fourths 
that of rye, while wheat and beets are intermediate. 
WIDTSOE S EXPERIMENTS. 
Widtsoe (1909) gives the average water requirement found for 
each of the crops used during the 4-year period covered by his experi- 
ments. (Table XVII, p. 28.) The results obtained using " College 
loam" soil may be considered as representing the water requirement 
of crops at Logan, Utah, when grown in productive soils. Widtsoe 
gives the following values for the water requirement of crops in this 
soil: Corn, 386; wheat, 546; sugar beets, 497; and peas, 843. These 
results are in agreement with those obtained by the writers in north- 
eastern Colorado, with the exception of sugar beets, the water require- 
ment of which is 32 per cent higher than the ratio obtained there. 
leather's experiments. 
Leather (1910, 1911) has measured the water requirement of a num- 
ber of crops at Pusa, India. His experiments were carried on in 
glazed stone jars of various sizes, 9 or 12 inches in diameter and 
from 12 to 22 inches in depth, ranging in capacity from 12 to 48 
kilograms of soil. The jars were not covered, the loss of water from 
the soil being estimated by the use of check jars in which no plants 
were grown. When a number of crops were grown in the same soil, 
four blank jars, two of which contained manured soil, were used, and 
the arithmetical mean of the losses taking place from the four jars 
was assumed to represent the amount of water which evaporated 
directly from the soil during the experiment. 1 
i Leather cites in illustration four blank jars which lost 9.93, 10.68, 13.03, and 14.11 kilograms, respec- 
tively, during the growing period. He states that the differences are not attributable to the presence of 
manure. The probable error of a single determination as calculated from the above figures is 1.6 kilograms. 
The water transpired by juar with different treatments during the period covered by the above figures is 
as follows: Unfertilized, 3.4 and 6.7 kilograms; with nitrogen, 6.2 and 7.1 kilograms; with nitrogen and 
phosphoric acid, 36.1 and 28.1 kilograms. The probable error of the evaporation correction thus amounts 
to about 5 per cent of the total transpiration in the case of the thrifty plants. With the unfertilized plants 
it is 47 and 24 per cent, respectively. This uncertainty arises from the differences in the evaporation from 
blank jars even when they are treated alike. A further error which can not be estimated results from the 
fact that the soil in the culture pots is shaded and dried by the plants growing in it. 
l'S5 
