1901.] 



PUBLIC DOCUMENT — No. 33. 



119 



The Relative Value for Green Manuring of the 

 Soy Bean and Cow Peas. 

 So much has been ^^^ concerning the vahie of cow peas 

 for green manuring yk/i "'fes that it has seemed desirable to 

 compare this crop withtaie soy ])can for that inirpose. Ac- 

 cordingl}^ two varieties of cow peas, the Wonderful and the 

 Black, the former a late and the latter an early variety, have 

 been grown under conditions allowing comparison with the 

 medium green soy be?/^- The growth of all the crops was 

 good and each occuf^^^r about onc-tifth of an acre. The 

 Wonderful cow pea w/^on cut had only just begun to blossom, 

 the Black had l)ut a siiiall proportion of its pods ripe, while 

 all the pods on the soy bean were practically mature. The 

 following table shows the results : — 



Cow Peas and Soy Beans for Green Maimriurj. 



VARIETF. 



Pounds per Acke. 



Oreeii 

 Weight. 



M?t?er. Nitrogen. 



Wonderful cow pea, . 

 Black cow pea, . 

 Medium green soy bean, 



19,600 

 20,035 

 19,685 



3,622 

 3,389 

 5,386 



80.4 



62.1 



167.3 



It will be noticed that the soy Ijcan furnished much larger 

 quantities both of dry matter and of nitrogen than either of 

 the varieties of cow peas. It gave practically three-fifths 

 more dry matter and more than double the nitrogen furnished 

 by the better of the two varieties of cow peas. The roots 

 of the bean were thickly studded with nodules, as also were 

 the roots of the cow peas ; and both must, therefore, have 

 possessed the al)ility to draw upon the atmosphere for a con- 

 siderable part of their nitrogen. It appears impossible to 

 doubt that the manurial value of the soy beans must have 

 been far greater than that of either of the varieties of cow 

 peas. 



In estimatiug the significance of these results, it should be 

 kept in mind that the soil was a medium loam, retentive of 

 moisture, and that the season had a fairly well-distributed 



