272 CROP ROTATION 



the typical soil of the Red River Valley, spring wheat yields best 

 when preceded by corn, potatoes, mangels, peas and clover; and 

 when preceded by oats, barley, spring rye and flax, the yield was 

 practically the same as when wheat was grown continuously. 



Winter wheat does weU after early potatoes, clover, alfalfa, 

 soybeans and pasture. Onions do best after onions, except when 

 certain insects or diseases become injurious. Corn usually suc- 

 ceeds best after clover, alfalfa and pasture. Oats on rich lands 

 stand up better and 3deld best when they are grown after such 

 crops as corn, wheat, barley and cotton. These are but a few illus- 

 trations to emphasize the importance of considering carefully the 

 best combination of crops for rotation, and the place each crop 

 should occupy in the rotation for best results. 



Factors Determining a Good Rotation. — It follows that there 

 are two factors which determine a good rotation, viz., a proper 

 combination of crops, and the order in which these crops should 

 be grown. 



Proper Combination of Crops. — In general, the benefits of 

 rotation can best be attained when the cropping system includes 

 (a) a cultivated crop, (6) a grain crop, and (c) grass, clover or some 

 other legume. 



The growing of a cultivated crop aids in weed control, and 

 in many instances improves the physical condition of the soil 

 and prepares the land for the crop following. Corn, for example, 

 is often grown two years in succession on blue-grass sod to eradicate 

 the blue-grass in preparing the land for alfalfa. A cultivated crop 

 also prepares the ground for grain. 



The growing of small grain in the rotation greatly facilitates 

 the seeding of grass, clover, etc., without losing the use of the land 

 during the time required for the grass or clover seeding to become 

 established for use as hay or pasture. In addition to their value 

 as grain crops, fall-sown grains may serve as catch and cover crops, 

 and frequently as winter pasture crops, of particular value in 

 the South. 



No rotation can give best results without a legume. Experi- 

 ments show that crops can be produced most economically only 

 when clover or some other legmne is grown in rotation with them. 

 In a twenty-year test at the Ohio Station, it was found that the 

 average cost of the commercial fertilizers per bushel increase in 

 yield was forty cents for -corn, sixty-six cents for oats, and sixty- 

 nine cents for wheat, when these crops were grown continuously 



