CHEMISTRY OF CROP. 



261 



3 per cent., in the straw about 5 per cent., and in the pod 

 about 7 per cent. 



The composition of the inorganic (mineral) matter may 

 be taken as follows : 



These analyses show us the large proportion of lime 

 which the pea requires to enable it to carry out its pro- 

 cesses of growth and reproduction ; and if this lime be not 

 naturally present in the soil, or be added to it in the shape 

 of manure, as phosphate or sulphate of lime (gypsum), or 

 in the shape of amendments, as marling, liming, or chalk- 

 ing, the cultivation of peas cannot be successfully carried 

 on. At the same time, they show that the crop requires 

 large supplies also of potash and phosphoric acid, which 

 can only be obtained in a soil in a high state of cultiva- 

 tion; and if these points are not secured, the crop must be 

 proportionably diminished. The ingredients removed from 

 the soil by a crop of peas are the same as those removed 

 by the bean crop, though the total quantities are some- 

 what less, as the straw of the bean contains a higher pro- 

 portion of mineral substances than that of the pea. For 

 all practical purposes, however, the tabulated quantities 

 given at p. 240 will serve for both crops. 



The organic analyses of peas and of pea straw at once 

 indicate their high feeding properties, and thus confirm 



: The mean of several analyses. 



5 Hertwin 

 18 



