88 SOILS AND FERTILIZERS 



mal and vegetable matter incorporated with soils un- 

 dergoes decomposition there is a union of some of the 

 organic compounds with the base-forming elements of 

 the soil. The decaying organic matter produces or- 

 ganic 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. 17 



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

 Humic acid -)- potassium sulphate potassium humate, etc. 



The fact that a union occurs between the organic 

 matter and the soil has been demonstrated by mixing 

 with soils known amounts of various organic mate- 

 rials, as cow manure, green clover, meat scraps, and 

 sawdust, and allowing humification to go on for a year 

 or more. After humification has taken place, the 

 humus extracted from the soil contains more potash, 

 phosphoric acid, and other elements than were present 

 in the humus of the original soil and humus-forming 

 material, showing that a chemical union has taken 

 place between the decaying organic matter and the soil. 

 The power of various organic substances to produce 

 humates is illustrated in the following table. 29> 8s 



Humic phos- Humic 



phoric acid. potash. 



Cow manure humus : Grams. Grams. 



In original manure and soil 1.17 1.06 



In final humus product (after hu- 

 mification) 1.62 1.27 



Gain in humic forms 0.45 0.21 



Green clover humus : 



In original soil and clover 3.21 5.26 



In final humus product 3.74 4.93 



Gain in humic forms 0.53 (Loss) 0.33 



