96 SOILS AND FERTILIZERS 



Nitrogen and Ash Elements. 16 



In six oat In six mature 



seeds. plants. 



Gram. Gram. 



Nitrogen 0.0040 0.0556 



Potash 0.0013 0.0640 



Soda 0.0001 ^0079 



Lime 0.0002 0.0249 



Magnesia 0.0005 °- 01 IO 



Iron 0.0064 



Phosphoric anhydride 0.0016 0.0960 



Sulphuric anhydride 0.0001 0.0090 



Silicon 0.0026 0.7300 



The fact that plants feed on humate compounds, 

 and that decaying animal and vegetable matter pro- 

 duce humates from the inert potash and phosphoric 

 acid of the soil, has an important bearing upon crop 

 production, because it indicates a way by which inert 

 plant food may be converted into more active forms. 

 It also explains that stable manure is valuable because 

 it makes the inert plant food of the soil more available. 



102. Amount of Plant Food in Humate Forms. — 



In a prairie soil containing three and five-tenths per 

 cent, of humus there are present 100,000 pounds of 

 humus per acre. Combined with this humus there 

 are from 1,000 to 1,500 pounds each of phosphoric 

 acid and potash. Soils which have been under long 

 cultivation without the restoration of any humus 

 contain from 300 to 500 pounds each of humic potash 

 and phosphoric acid. 17 A decline in crop-producing 

 power has in many cases been brought about by the 

 destruction of the humus. 



