IO4 SOILS AND FERTILIZERS 



by extracting the soil with a dilute alkali, as ammonium 

 hydroxide, after treating with a dilute acid to remove 

 the lime which renders the humus insoluble. 



114. Humification and Humates. When the animal 

 and vegetable matter incorporated with soils undergoes 

 decomposition, there is a union of some of the organic 

 compounds with the base-forming elements. The decay- 

 ing organic matter produces organic products of an acid 

 nature. The organic acids and the base-forming 

 products unite to form humates or organic salts, which 

 are neutral bodies. This process is humification. 18 



Humic acid + calcium carbonate = calcium humate + CO 2 . 

 Humic acid + potassium chloride = potassium humate and solu- 

 ble chlorides. 



That a union occurs between the organic matter and 

 the soil has been demonstrated by mixing with soils 

 known amounts of definite organic compounds and 

 various organic materials, as cow manure, green clover, 

 meat scraps, and sawdust, and allowing humification to 

 go on for a year or more. After humification had 

 taken place, the humus extracted from the soil con- 

 tained more potash and phosphoric acid, than were 

 present in the humus of the original soil and the humus- 

 forming material, showing a chemical change had taken 

 place between the organic matter and the soil. The 

 power of various organic substances to produce humates 

 is illustrated in the following table : 18> 85 



