Rotation of Crops ,101 



Fig. 50a. Oats grown on soil previously 

 sown to mustard and vetch. 



will be very beneficial to the grain; 'but not so necessary 

 to the others. Fig. 50a shows the difference in a crop 

 of oats grown on soil previously green-manured with a 

 crop of mustard (a non- 

 legume) and when green- 

 manured with a crop of 

 vetch. This result shows 

 strongly the need of in- 

 cluding some legume in 

 any sort of rotation. In 

 some soils cover crops or 

 heavy applications 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 washing and leaching than 

 when occupied by plants. It is often possible to grow a 

 quick-maturing crop after the principal crops have been 

 harvested, 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- 



