Rotation of Crops 99 



will be very beneficial to the grain, but not so necessary 

 to the others. In some soils cover crops or heavy appli- 

 cations of fresh manure tend to cause too rank a growth 

 of straw in the small grains. In such cases it is advisable 

 to allow a crop of corn to come before the small grains. 



144. Cover Crops ; Catch Crops. Except in arid 

 regions, it is best to keep the land constantly occupied by 

 some crop. They not only keep the land continually earn- 

 ing something, but it is best for the land. A field that is 

 bare or fallow loses more by leaching than when occu- 

 pied by plants. It is often possible to grow a quick- 

 maturing crop after the principal crops have been harves- 

 ted, for example, June corn after potatoes or small 

 grain; cowpeas after corn. 



145. Marketable, or Usable, Crops. In planning a 

 rotation or selecting a cover crop, it is necessary to con- 

 sider what may be successfully sold, or used to advan- 

 tage. This will depend on the markets and the farmer's 

 facilities for keeping and feeding certain kinds of crops. 



146. Other Advantages of Rotation. Besides pre- 

 serving the soil nutrients, providing for their better dis- 

 tribution, facilitating fertilizing, rotation (which is 

 closely related to diversification) affords other ad- 

 vantages: 



(a) Tends to free the land from noxious weeds, as where 

 oat stubble is planted to June corn, the late cultivation 

 of the corn prevents the seeding of the weeds, such as 

 cockle burs or Johnson grass. 



(b) Exterminates insect and fungous diseases. Insect 

 and fungous pests usually attack only particular kinds of 

 crops. If the same crop is grown on the same land year 

 after year, the larvae of insects and spores of the fungi 

 lodging in the ground during the fallow season will 



