4 BULLETIN 512, U. S. DEPARTMENT OF AGRICULTURE. 
soil will absorb 2 inches of rainfall. The incorporation of organic 
matter or humus in a soil adds materially to its moisture-holding 
capacity. This is best accomplished by plowing under deeply, ma- 
nure, stubble, stalks, and various cover crops. This organic matter, 
in a decomposed state, is capable of absorbing considerable water and 
forms a richer and deeper top soil. 
USE OF COVER CROPS. 
Vegetation or cover crops will protect the soil in four ways: (1) 
by holding rain water on the surface for a time, thus giving the 
soil a better opportunity to absorb the water; (2) by keeping the soil 
open through the growth of the roots, which form passages for the 
water to reach the subsoil; (8) by holding the soil particles together 
through the binding power of the roots; and (4) by reducing the 
movement of soil particles through diminishing the velocity of sur- 
face water. Cover crops usually are grown during the winter or 
when the land is not being used for other crops. Their importance 
as a means of protecting land from erosion at such times can not be 
emphasized too strongly. Vetch, clover, cowpeas, wheat, and rye are 
used commonly for this purpose. It can be said generally that good 
farming and the use of cover crops go hand in hand. 
PRACTICE OF LEVEL CULTURE. 
Contour plowing and the following in general of practically level 
lines in farm operations tend to check the surface flow down a slope 
and to retain the water where it falls. In cultivating crops each 
row is banked up and a shallow depression which holds the surface 
water is left between the rows. Thus the absorption by the soil of 
this impounded water is facilitated and the rapid run-off down the 
slope, with its destructive eroding power, often is entirely eliminated 
in case of ordinary rains. Contouring contributes also in a consider- 
able degree to the conservation of moisture on hill lands. The very 
apparent benefits of this practice merit its universal use on lands sub- 
ject to erosion. 
PASTURING AND FORESTING. 
Often it seems impossible to prevent erosion on lands with exces- 
sive slopes. No attempt should be made to cultivate such areas but 
they should be seeded to meadow or pasture and usually retained as 
such. In well-sodded land the soil is not exposed directly to the 
erosive action of the water, so that erosion is much less destructive 
than in cultivated fields. 
In many sections of the country timberland on excessively steep 
slopes has been cleared for cultivation, and in many instances after 
