160 The Commercial Apple Industry 



By combining cover-crops with cultivation, it is possible 

 to secure nearly all of the benefits to be derived from the' 

 varying 1 methods of soil treatment. Such a system is 

 designed to preserve and promote permanent soil fertility. 



CQVEB-CBOPS 



There are two important kinds of cover-crops: (1) 

 leguminous, such as alfalfa, clover, peas, vetch and beans; 

 (2) non-leguminous, such as rye, rape and buckwheat. 

 These crops may be further subdivided into those which 

 live over the winter, such as clover, vetch and rye, and 

 those like rape, buckwheat and peas which die down in the 

 fall. Leguminous crops are recommended at least once in 

 three years or more often, especially when trees are not 

 making sufficient annual growth and when foliage is pale. 

 As a general rule, they are preferable to non-leguminous 

 crops since they add nitrogen to the soil. Cover-crops 

 which live through the winter protect the trees against 

 winter-injury in the absence of snow and also prevent 

 the washing and leaching of soluble plant-foods. 



Alfalfa is by far the most popular cover-crop in western 

 irrigated orchards where it has largely supplanted the 

 clean culture system. Vetch, clover and other cover-crops 

 are also recommended. Although alfalfa is known in the 

 West as a cover-crop, a distinction should be made between 

 the eastern cover-crop planted in the fall and plowed under 

 the following spring and the western cover-crop which is 

 left in the orchard for several years. In reality the west- 

 ern cover-crop is an inter-crop, but since its purpose is 

 primarily to benefit the orchard rather than to provide 

 immediate returns to the grower, the word cover-crop has 

 been retained. 



