GREEN MANURES 



29 



a group of plants that not only perform these tAvo functions, but 

 are able, through the aid of bacteria working on their roots, to 

 secure nitrogen from the air and add it to the soil. This group of 

 plants is known as legumes, and includes clover, alfalfa, cow peas 

 (Fig. 12), soy beans, vetch, and others. 



One of the best of these plants for green manuring in connection 

 with vegetable growing is hairy vetch. It can be sown from July 

 15 to September 15, and will grow until the ground freezes in 



Fig. 13. — Four-horse load of manure near Boston. 



fall. It lives over winter and resumes growth in spring. As in the 

 case of rye, early soAvings may be plowed under in the fiill or later 

 sowings in the spring. 



In the South, cow peas and soy beans may be grown as green 

 manuring crops in the sunmier, to prepare the land for grooving 

 vegetables in the fall, winter or early spring. In some forms of 

 truck-growing where the vegetable crop occupies the land only 

 one season in a three- to six-year rotation, clov(»r or alfalfa pre- 

 ceding the vegetables serves the purpose of a green manuring crop 

 for the vegetables. If a heavy growth of clover can be plowed 

 under, rather than merely the sod, it is usually a decided advantage. 



