CROP ROTATION 25 



year rotation containing two or three years of a sod 

 producing legume crop is desirable. A dark colored, 

 fertile soil may well grow more cultivated and small 

 grain crops. 



Buckwheat or flax are poor crops to precede a small 

 grain crop. There is apparently some injurious effect 

 produced by these two crops which is entirely separate 

 from any question of plant food or physical condition of 

 the soil. 



Wheat does well following a cultivated crop and espe- 

 cially well if this is a legume such as beans or peas. Oat 

 stubble is a good site for wheat if the ground is prepared 

 immediately after the oats are off. 



Alfalfa should be sown without a nurse crop. Most 

 grasses and clover, if sown in the spring, do best with a 

 nurse crop. Wheat, barley, or oats make a good nurse 

 crop. 



It is a good plan to arrange a place or two in the rota- 

 tion for short time catch crops to be plowed under as 

 green manure or source of nitrogen supply. 



24. Rotation does not maintain fertility. — Although 

 much may be said in favor of crop rotation, we need to 

 guard against the erroneous impression that a systematic 

 rotation of crops is in itself sufficient to maintain the 

 fertility of the soil and insure good crop yields indefi- 

 nitely. This theory has gained acceptance by some and 

 has occasionally found expression in magazines and farm 

 papers. The advocates of this theory provide only 

 that the rotation include crops adapted to the soil in 

 question, that some legume be grown, and that good culti- 

 vation and drainage be provided. The data given in 

 the early part of this chapter is convincing evidence 

 against any such teaching. 



