34 The Bulletin, 



there would be as much improvement of the soil and increase in 

 after crops from removing the hay as there would be if the entire 

 plant were left. This is entirely erroneous. From 80 to 88 per cent 

 of the fertilizing or soil-improving value of the cowpea is contained 

 in the hay and peas which go with it, and 12 to 20 per cent remain 

 in the roots and stubble. Different vareties vary in the proportions 

 of hay and peas and roots and stubble. Our investigations now in 

 progress include a further study of these questions for the purpose of 

 throwing additional light on this phase of the problem of soil im- 

 provement from gi'owing cowpeas. Since around 85 per cent of the 

 soil-improving part of the cowpea is removed in the hay and peas, 

 the large hay-producing vareties are the best for soil improvement. 

 With this as our criterion, which is the correct one, the following 

 vareties of peas are specially desirable for soil improvement : 



Unknown, 



Iron, 



Clay, 



Brown Coffee, 



Whipporwill, 



Red Crowder. 



Fertilization.— A& the cowpea is able to get a portion of its nitro- 

 gen from the air, it is not necessary on soils in fair to good condition 

 to supply this constituent in fertilizers for this crop. Our experi- 

 ments confirm this view. Other experiments and observations indi- 

 cate that where nitrogen is supplied in the fertilizer or is contained 

 in too great abundance in the soil, the cowpea may become lazy and 

 is not as active in extracting nitrogen from the air as when it is 

 necessary for it to obtain it from this source for its gi'owth. On poor 

 soils, where the plants start slowly and are sickly in appearance, it is 

 profitable to add a small amount of nitrogen in the fertilizer, or, as 

 a side dressing, to produce growth to the point where the root de- 

 velopment will enable the peas to get the nitrogen they need from 

 atmospheric sources. 



On soils needing lime because they are deficient in it, or where 

 they need lime to correct sourness or acidity, it should be applied. 



The two important fertilizer constituents for the cowpea are phos- 

 phoric acid and potash, and it pays to supply these liberally, either 

 combined or singly, according to the needs of the soil, as the plant 

 can not make a satisfactory growth and add to the fertility of the 

 soil without them. 



A ton of pea-vine hay, in round numbers, removes from the soil 



47 pounds nitrogen, 



10 pounds phosphoric acid, and 



29 pounds potash, and 1 bushel of peas with the hulls going with 

 them (85 pounds) removes 2.3 pounds nitrogen, .0 pound phos- 



