20 THE__^COW PEA. 



rather than to the cow pea which does so gather it for itself. 

 It appears that when the cow pea grows on a soil naturally 

 rich and well supplied with nitrogen, the plant becomes 

 "lazy" and draws from the nitrogen already in the soil be- 

 fore exerting its natural and peculiar power of collecting ii 

 from the air by means of the little nodules on its roots. Thus 

 every habit and characteristic of the plant shows that the 

 true economy of the cow pea is to restore poor land and 

 make use of potash and phosphoric acid rather than to de- 

 plete good land and use nitrogen which can be employed to 

 better advantage in producing other crops which need it 

 more. From discussing fertilizer for cow peas, or other 

 crops, no unvarying rule can be formulated. Soils differ so 

 much that a mixture giving good results on one field may 

 fail or be wasteful on another. Fields on the same farm, 

 often those lying side by side, differ in their crop re- 

 quirements. One experiment at the Delaware Experiment 

 Station showed that where i6o pounds of muriate of potash 

 were used per acre the yield of cow pea vines was doubled, 

 while phosphoric acid was apparently without effect. Here 

 was a soil naturally strong in phosphoric acid, yet it would 

 not be safe to accept this result as a sure rule for general 

 fertilizing. On most soils of low-producing power, potash 

 is a most useful element for the cow pea, but phosphoric 

 acid is also more or less needed. The one great object of 

 fertilizing is fully to supply the mineral needs of the plant, 

 guided by the well established principle that when these are 

 supplied in abundance there is a corresponding gain it 



