22 



PRINCIPLES OF AGRICULTURAL CHEMISTRY 



is rich in potash and lime, but contains much smaller quantities 

 of magnesia and phosphoric acid. The quantity of silica is larger 

 than in the ash of seeds or tubers, being slightly less than the 

 phosphoric acid. 



Cereal straws are variable in ash content, though the ash is con- 

 siderably lower than in leaves. The ash is very rich in silica, and 

 contains fair amounts of potash. Its content of lime and magnesia 

 is comparatively small, and it contains about half as much phos- 

 phoric acid as leaves. Like leaves, cereal straws contain more 

 lime than magnesia. 



Leguminous straws resemble leaves closely. The ash is rich 

 in lime and potash, and contains approximately the same amounts 

 of phosphoric acid and magnesia as the ash of leaves. 



AVERAGE AMOUNT OF ASH CONSTITUENTS IN 1000 PARTS BY 

 WEIGHT OF THE DRY SUBSTANCE. 



