SOIL TILLAGE AND CROP ROTATION 255 



tiny root hairs with moisture and materials for growth. 

 The important tune for deep tillage is before the crop 

 is planted. 



Surface tillage is necessary to keep the upper layer 

 of soil in good condition, to check the growth of weeds, 

 and to prevent the evaporation of soil moisture. The 

 latter result is accomplished because proper surface 

 tillage produces a so-called dust mulch which prevents 

 evaporation from the soil below. The important time 

 for surface tillage is after the crop has started into 

 growth. 



Crop Rotation 



The rotation of crops is one of the best ways of con- 

 serving the fertility of the soil. When this is practiced 

 one crop follows another in the same field, so that for a 

 series of years no single crop shall be planted for two 

 successive seasons. A common succession is to follow 

 corn with wheat and wheat with clover, so that for a 

 series of three years the field will be planted the first year 

 to corn, the second year to wheat, and the third year to 

 clover, the latter being plowed under after it has been 

 growing one or two seasons, when the field may again be 

 planted to corn. In different regions different systems 

 of rotation are practiced. 



There are many advantages in a proper system of 

 crop rotation. One of the most important of these is 

 in the ability to enrich the land by plowing under clover 

 or some other leguminous crop which gathers nitrogen 

 from the air. The principal legumes used in this way 

 are red clover, crimson clover, alfalfa, cow peas, and 

 the vetches. Each of these crops is able to gather free 



