DECOMPOSITION OF FARM MANURE 261 



starch, cellulose, other carbohydrates, lignin, fat, proteins 

 in various stages of decomposition, mineral elements com- 

 bined organically, remains of intestinal juices, and other 

 compounds. The liquid portion contains organic and in- 

 organic salts, soluble nitrogenous compounds like urea, etc. 

 The litter, of course, contains the usual plant compounds 

 present in such materials. 



200. Bacteria in Manure. — Liquid excrement when first 

 voided contains no bacteria, but the solid excrement con- 

 tains exceedingly large numbers, determinations on various 

 excrements showing from 90,000,000 to 150,000,000 organisms 

 in one gram of material. In addition to this, litter contains 

 from 10,000,000 to 400,000,000 organisms. In the course 

 of time the number of organisms diminishes as food becomes 

 scarcer and the products of their activities increase sufficiently 

 to kill many of them. 



t/ 



201. Decomposition of Farm Manure. — As a result of its 

 high bacterial content, manure commences to decompose as 

 soon as it is produced. Molds also help the decomposition. 

 The bacterial changes which take place in it are of consider- 

 able importance and can be discussed best under two heads: 

 Aerobic, where air has free access to the materials; and 

 anaerobic, where air is kept out. 



(a) Aerobic. — The most important changes taking place 

 in manure are those affecting nitrogen.. This element is 

 present in the urine largely as urea, CO(NH 2 ) 2 , which is 

 attacked very easily by several kinds of bacteria. The 

 action is one of hydrolysis, thus: 



CO(NH 2 ) 2 + 2H 2 = (NH 4 )2C0 3 . 



The ammonium carbonate readily breaks up on exposure 

 to the air, as follows: 



(NH 4 )2C0 3 ^2NH 3 + CO2 + H 2 0. 



This results, of course, in loss of nitrogen, for the ammonia 

 escapes into the air. The reaction is reversible, and in the 

 presence of plenty of carbon dioxide and water with no 

 circulation of air to remove the volatile products, ammonium 

 carbonate is not decomposed. 



