STORING WATER IN THE SOIL 115 
smaller proportion reaches the greater soil depths. 
In the Great Plains district, therefore, greater care 
will have to be exercised dirine the summer in secur- 
ing proper water storage than in the Great Basin, 
for instance. The 
principle is, never- 
theless, the same. 
Burr, working under 
Great Plains condi- 
tions in Nebraska, 
has shown that the 
spring and summer 
rains penetrate the 
soil to the depth of 
6 feet, the average 
depth of the borings, 
and that it undoubt- 
edly affects the soil- 
moisture to the 
depth of 10 feet. 
In general, the dry- 
farmer may safely 
accept the doctrine 
that the water that 
falls upon his land 
UZ, CZ 
Uy "ia VEZ 
Fic. 30. Diagram to illustrate the degree 
and depth to which the precipitation 
of fall, winter, and earliest spring is 
found in the soil at seed time. Lines 
on the left indicate the percentage of 
water in the soil in the fall; those on 
the right, the percentage of water in 
the soil in the spring at seed time. 
penetrates the soil far beyond the immediate reach 
of the sun, though not so far away that plant roots 
cannot make use of it. 
