306 



FIELD CROP PRODUCTION 



is a summer annual with a branched, upright, rather 

 woody stem, which grows from 2 to 3J feet or more in 

 height. The leaves are trifoliate, rather large, and quite 

 abundant. The flowers, which are clustered in the axils 

 of the leaves, are small and inconspicuous and are either 

 white or purple in color. Soy beans are ordinarily self- 

 pollinated, although 

 insects may produce 

 cross-pollination. 

 The pods, when they 

 develop, are short as 

 compared with those 

 of the cowpeas, being 

 from 1 to 2| inches 

 in length, containing 

 from 2 to 4 seeds. 

 The stems, leaves, and 

 seed pods are covered 

 with short hairs, usu- 

 ally reddish brown in 

 color. In general ap- 

 pearance the soy bean 

 is more like the peas 

 than like the beans. 



Fig. 111. — A soy bean plant. 



The root system of the soy bean consists of a large tap 

 root, with comparatively few lateral branches. The root 

 growth is rather slight when compared with that of most 

 of the other legumes, but the tubercles that are formed 

 on them are large and abundant. 



There are almost a hundred varieties of soy beans 

 grown in the United States. They vary greatly in the 

 character of the plant, size and shape of the seed, and in 

 the length of season required for their growth. Many 



