streams which have power to cut ditches, but follows the culti¬ 
vated rows such as corn or potatoes or the drill rows of grain 
fields and the soil is removed only from the knolls and deposited 
in the hollows. 
Contour cultivation and arrangement of the crop rows across 
the slope instead of with or down the slopes retards the move¬ 
ment of soil in such fields. Keeping the most exposed places 
in sod as much as possible and the cultivation of the field in 
alternate strips of crop and sod across the slopes are incon¬ 
venient but often necessary methods. 
Rotation of crops in such a way that two cultivated crops 
do not follow in succession gives the field opportunity to recover 
from its losses under cultivation and avoiding a hard bare con¬ 
dition of the eroded ground after harvest as much as possible 
prevents surface wash in the fall. A cover or catch crop of 
rye or peas in the corn rows helps protect the soil after harvest 
and furnishes pasture until winter. 
Deep plowing and plowing under of straw, manure, or a 
second crop of clover to increase the organic matter in the soil 
also give the surface of the field greater absorbing capacity and 
resistance to erosion. 
Gullying occurs where greater volumes of water collect form¬ 
ing cutting-streams where steeper slopes cause the water to 
flow faster or in places where the soil has an unstaple founda¬ 
tion of sandy material which easily undermines when the water 
once cuts through the surface soil and establishes a fall which 
cuts back in the sandy subsoil. In some situations large gullies 
one half mile or more in length are sometimes cut during a 
single season. 
In their beginnings most small gullies are easily handled. 
Small drainage-ways or shallow ditches can be filed with straw 
or manure and plowed shut. Such shallow drainageways should 
be left in permanent sod. The plow can be easily thrown out 
in passing across them. On the level terraces or where heavy 
soil lies on light sand or sandy gravelly subsoil, small ditches 
must be immediately tended to because all ditches on such soil 
are dangerous. 
Where the subsoil is clay and where clay or silt soil material 
is being brought down by the flood water, large gullies may 
be made to fill by putting in a dam of stumps, brush, and logs. 
Where the subsoil is sandy much greater care is required. If 
