SOIL EEOSION IN THE SOUTH. 21 
is eithor covered with a layer of sand or is scoured into ditches and 
smaller channels, impairing the agricultural value of the land. 
In some of the districts of the South the gullies, which are ordi- 
narily dry, become filled with rapidly flowing water. This temporary 
stream carries a heavy burden of soil material, much of which is sand, 
as the soil conducive to the formation of these gullies is generally 
sandy. The velocity of the water is first checked in the valley 
and the sand is largely deposited. A formerly productive field 
covered in this way with a layer of sand 6 inches to 2 feet in thick- 
ness is shown in Plate IX. 
AGRICULTURAL PROBLEMS. 
As previously pointed out, the greatest damage from erosion gen- 
erally occurs where the original growth has been removed and the 
land in being used for crop production. This most frequently means 
clean culture. The agricultural conditions in the South are espe- 
cially favorable for erosion, as the main crop is cotton, which requires 
entire freedom from grasses and weeds. The rotations practiced 
may include some other clean cultivated crop, as corn, but in a great 
many cases cotton is the only crop grown. 
The labor problem and other economic conditions have much to 
do with this system of farming. Ordinarily the small farmer and 
the tenant can obtain credit only by growing crops that can not be 
easily disposed of without the creditor's knowledge. The crop that 
meets all conditions best is cotton. Hence it of tens happens that 
the same land is cropped year after year to cotton, until the soil be- 
comes so unproductive that its cultivation is not profitable, when it 
is allowed to "lie out," and becomes infested with weeds. It is then 
that erosion is most destructive. The soil is exhausted of organic 
matter, and even before the weeds begin to grow the rains form 
gullies over the surface. Probably the field will not be put under cul- 
tivation again, and in a few years it becomes devastated, without 
agricultural value, and a menace to the surrounding land. 
The question of erosion must be considered in adopting crop rota- 
tions. In addition to the use of terrace and hillside ditches for check- 
ing the soil wash, it must be remembered that the incorporation of 
large quantities of organic matter produces an open, porous soil, 
capable of absorbing water, and that deep plowing furnishes a sub- 
soil reservoir for the storage of surplus water. It is not always pos- 
sible to practice these methods with certain crops, so that the ten- 
dency to erosion and the effects of certain practices must be con- 
sidered before a given crop is included in the rotation. The Georgia 
experiment station, 1 for example, has conducted experiments which 
indicate that plowing below 8 inches lessens the yield of cotton. 
It is also known that the quality of tobacco is injured by legume 
> Ga. Agr. Expt. Sta., Bui. 63, p. 124. 
