THE COW PEA. 



already present. The cow pea plant begins to take up 

 atmospheric nitrogen when its leaves develop, and on poor 

 soils, before this stage is reached, the young plants gener- 

 ally suffer from the lack of nitrogen. This poverty of nit- 

 rogen is indicated by a yellowish leaf, absence of vigor in 

 the plant and a general sickly appearance ; an application 

 of about 75 pounds of nitrate of soda per acre quickly 

 remedies the trouble. 



While an artificial application of nitrogen is regulated 

 by the circumstances described, there are no such condi- 

 tions affecting potash and phosphoric acid. Experiments 

 at the Louisiana Experiment Station show that one acre of 

 average cow peas contains 65 pounds of nitrogen, 11 1 

 pounds of potash and 20 pounds of phosphoric acid; of 

 this the roots and stubble alone contain 8 pounds of nitro- 

 gen, 18 pounds of potash and 5 pounds of phosphoric acid. 

 These figv 3s vary of course, with different yields, but the 

 range of variation is not wide and only serves to bring out 

 clearly and boldly the fact that with every pound of nitro- 

 gen, a certain amount of potash and phosphoric acid 

 is also assimilated by cow peas. These weights do not fix 

 absolutely the amount of plant food needed by cow peas, 

 but they do suggest approximately and relatively what the 

 crop draws from the soil and what even the least worn 

 fields have returned to them in the shape of plant food to 

 prevent the soil from gradually losing its fertility. Let it 

 be carefully noted, however, that there is, of necessity, some 

 waste in the application of fertilizers ; that not all the 



