SOYBEANS 527 



Ordinarily it is not advisable to sow soybeans until 

 about the time for planting corn, as soybean plants grow 

 but slowly during cool weather. Of 330 varieties grown 

 at Arlington Farm, Virginia, 2 were classified as very 

 early, maturing in 80 to 90 days ; 12 as early, maturing 

 in 90 to 100 days ; 40 as medium early, maturing in 100 

 to 110 days ; 76 as medium, maturing in 110 to 120 days ; 

 85 as medium late, maturing in 120 to 130 days ; 55 as 

 late, maturing in 130 to 150 days, and 60 as very late, 

 requiring more than 150 days. 



On account of self-pollination, soybean varieties show 

 but little variability. Of such important varieties as the 

 Mammoth, Ito San and Guelph, which have been grown 

 in the United States for many years, seed from different 

 sources planted at the same place gave results which 

 show that no change in the life period has taken place, 

 whether the seed was grown in the North or in the South. 

 In a few varieties, however, there is satisfactory evidence 

 to show that the life period of a variety changes, becoming 

 gradually shorter when grown northward, and gradually 

 longer when grown southward. 



641. Time to cut for hay. Soybeans may be cut for 

 hay at any time from the setting of the seed until the 

 leaves begin to turn yellow. The crop is best fitted for 

 hay when the pods are well formed. If allowed to stand 

 much longer than this the stems rapidly become woody 

 and the percentage of protein lower ; and if left too long, 

 there is much loss in leaves. In the development of the 

 plant from bloom to maturity there is a marked increase 

 in the percentage of fat, little change in that of carbohy- 

 drates, but a decided diminution in the percentage of 

 protein. The following table shows the variation in the 

 composition of soybean hay of the Mammoth variety at 

 different stages of development : 



