194 



NITROGEN, PHOSPHORUS AND POTASSIUM 



It is always best to turn the green crop immediately under. 

 In this work jointers and coulters are useful (Fig. 74). A chain 

 may also aid in getting the growth turned under the furrow slice 

 (Fig. 131). Sometimes disking before plowing is helpful. 



Green Manures for Cultivated Crops. It is a general practice 

 to follow green manures with cultivated crops such as corn, cotton, 



FIQ. 131. Turning under weeds with the aid of a chain. 



cane, tobacco, potatoes, etc. Cultivation favors the decomposi- 

 tion of the green crop, thereby rendering available more plant- 

 food elements. 



Green Manuring Necessary in Soil Improvement. In practi- 

 cally all soil improvement plans, green manuring occupies an 

 important place. In some cases the growing and plowing under of 

 a crop of buckwheat proves the best method in making possible 

 the regeneration of very poor or exhausted soils. Many sands are 

 so poor that rye is the only possible first crop. When the rye crop 

 is plowed under, it makes possible the growing of other green ma- 

 nuring crops, as soybeans, cowpeas, or mammoth clover, which, 



