DESCRIPTION OF THE SOY BEAN 397 



seed, they may be killed by fumigating in tight boxes or bins 

 with carbon bisulfid (Sec. 135). 



The most troublesome diseases are root knot and wilt, 

 which usually occur only on sandy soils along the Atlantic 

 Coast. The best preventive measures are rotation of crops 

 and the use of resistant varieties, such as Iron. 



505. Use in Rotations. Since corn and cotton are the 

 most important crops in the region where cowpeas are most 

 largely grown, all rotations are usually based on these two 

 crops. A good rotation is (1) cotton; (2) corn with cowpeas 

 sown with it; (3) winter grain sown after the corn is removed, 

 followed the next summer by cowpeas sown on the stubble 

 for hay or seed. Numerous variations of this rotation may 

 be devised, but if possible a crop of cowpeas should be turned 

 under and one harvested for hay or seed once in three years. 

 As the seasons are long and the crops make rapid growth in 

 warm weather, the plan of growing cowpeas after a grain 

 crop has been harvested is entirely practicable in the South. 



THE SOY BEAN 



506. Origin and Description. Much that has been said 

 regarding the cowpea applies equally well to the soy bean. 

 This plant was introduced into the United States in recent 

 years from Japan and China, where, like the cowpea, it has 

 been cultivated for many centuries. The growth is usually 

 erect, with stiff, hairy stems and numerous large, broad 

 leaves. The leaves, which are borne on long stems, consist 

 of three leaflets. The leaflets are from 2 to 3 inches long; 

 the width is about two-thirds the length. The flowers are 

 small, clustered in the axils of the leaves, and are usually 

 pale purple or lilac in color. The short, hairy pods contain 

 two or three round or slightly flattened seeds. The seeds 

 are usually black, green, or yellow; they range in diameter 



