The Storage and Use of Soil Moisture 51 
does not use the water to as great depth as it would had it de- 
veloped normally. Indications of this were observed in a number 
of plats in 1911. The crops were so damaged by the hot winds 
that they died while available water was within their reach, had 
they made normal devolopment. The water was not available in 
considerable amount but could have been used under normal con- 
ditions. The demand for water, under such extreme conditions, 
was greater than could be supplied from a soil so nearly dry and 
to a plant in a weakened condition. 
The type of soil is an important factor in determining the 
depth to which crops will feed. On a loose or a sandy soil that 
offers but little resistance to the penetration of the roots, a plant 
will send its roots to a greater depth than on a heavier soil that 
offers more resistance. A layer of gumbo or hardpan underlying 
the surface soil at no great depth will prove more or less im- 
pervious to plant roots and cause the crop to feed in the soil 
above. Shale or rock has the same effect but it is more marked. 
It is a matter of common observation that during dry seasons 
the crop will suffer first on those spots in the field where an im- 
pervious stratum of some kind comes nearest the surface. 
In the following tables are given data to indicate the depth to 
which some of the various crops send their roots and use the 
moisture. The per cent of water in the soil at seeding time and 
at harvest is shown. Summer tilled land was used in every 
test. This, in every test, gave available water in every foot- 
section to a depth greater than the plant would use it. By com- 
paring the water content of the soil at seeding and harvest times 
we can see to what depth water was used : 
