THE COW PEA. 43, 



The renovation of soils through the use of cow peas de- 

 pends:largely on the use to which they are .put. The stubble 

 and roots contain considerable fertilizer, and the nitrogen is 

 mostly gain ; but much potash and phosphoric acid are re- 

 moved in the crop taken off, and unless this loss be made 

 good by applications of mineral plant food, cow peas ae* 

 tually exhaust the soil. This point is important and needs a_l- 

 ways to be kept clearly in mind. Cow peas, in common- with 

 wheat, require plant food, notably potash and -phosphoric 

 acid; but .wheat requires nitrogen plant food, cow peas do 

 not. The whole difference between legumes and non- 

 legumes is stated in this one point of feeding. Among 

 legumes, the cow pea stands first and pre-eminent as a crop 

 producer of fertilizer nitrogen. It may be grown between 

 crops of wheat and thus furnish nitrogen for many successive 

 crops. 



The soil improvement is well illustrated by an exami- 

 nation of the foregoing table. A ton of timothy hay 

 contains 25 pounds of nitrogen, 18 pounds of potash and IQ 

 pounds of phosphoric acid. All this must be supplied by 

 the soil. A ton of cow pea;-hay "contains 40 -pounds of 

 nitrogen, 30 pounds of potash, and 10 pounds of phosphoric 

 acid, of which only the latter two need be supplied by. the 

 soil. Suppose both are returned to the soil in the shape of 

 farmyard manure: estimating roughly, in the case of timo- 

 thy, the soil receives back what it gave to the timothy, but 

 in that of the cow pea, it receives not only what it gave, bulb 

 40 pounds of nitrogen in addition thereto. 



