234 AGRICULTURE 



portions left behind. And it is just this organic matter and 

 the finer soil particles that contain the best part of the plant 

 food. No wonder then that the hilltops have a thin poor 

 soil, and that the valleys are noted for their fertility. 



Prevention of erosion. While soil erosion can not be 

 wholly prevented, it can be greatly checked. And nature 

 suggests one effective remedy in covering all soil with vege- 

 tation. It is bare soil that washes and blows away. Even 

 a steep hillside when covered with grass is reasonably free 

 from erosion. For the stems tend to delay the downward 

 rush of water, thus causing it to soak into the ground, and 

 the roots bind the soil together. This indicates that steep 

 slopes should be used for pasturage and meadows rather 

 than for cropping. The addition of organic matter in the 

 form of manure also lessens the danger from washing, since 

 it increases the capacity of the soil to absorb water, and 

 also tends to bind the soil together. 



Hillsides when tilled sho'uld be plowed along the slope 

 rather than up and down, and in some sections it is neces- 

 sary to terrace the hillsides. This delays the forming of 

 rivulets and favors absorption of water. Every furrow 

 leading down the hill is the beginning of a gully in heavy 

 rains. Even the marks left by the wheels of a corn planter, 

 unless leveled over by harrowing, will serve as water chan- 

 nels and result in waste of soil and washing out of the seed 

 or plants. 



Gullies once started should be leveled immediately by 

 use of the plow or other form of cultivation. Packs of 

 straw, hay, or manure at the head of the channel, or at 

 intervals along its course, will do much to stop the erosion, 

 if used in time. Sheet, or surface, washing is, however, a 

 source of greater damage than the formation of gullies. 

 For sheet erosion, though gradual, is constant on the slopes 

 of all tilled fields. 



