308 Manures, Composts, Green Manures 



and easily soluble nitrogenous compounds in the manure diminish 

 rapidly after its application to the soil. This was originally believed 

 to be due either to denitrification or to a removal of the nitrogen to 

 the subsoil. It was later found that large parts of these soluble 

 forms of nitrogen are transformed into insoluble forms by the micro- 

 organisms responsible for the decomposition of the carbohydrates. 

 Only about a third of the nitrogen and a third of the phosphoric 

 acid in the manure were found to be made available to the growing 

 crops during the first 2 years after application of the manure; 70 

 per cent of the potash was made available in that time. 



Barthel and Bengtsson freed stable manure from ammonia by 

 distillation. When the manure thus treated was added to the soil, 

 no nitrate was formed; this tended to prove that ammoniacal nitro- 

 gen and urea nitrogen in the manure, but not the nitrogen present in 

 the form of organic compounds, undergo active nitrification. The 

 organic nitrogen was believed to be tied up in the manure in a form 

 unavailable for growth of higher plants. According to Egorov, one- 

 half to two-thirds of the nitrogen in the solid excreta of the manure 

 is in the form of microbial cell substance. By fixing the nitrogen in 

 their cells, during the process of decomposition of manure, fungi and 

 other microorganisms are thus able to reduce the losses of nitrogen. 

 Moisture and aeration exert an important effect upon the rapidity 

 and nature of the decomposition. This is illustrated in the compost- 

 ing of fresh horse manure (Fig. 54). 



Although fresh stable manure contains an extensive population of 

 characteristic microorganisms, especially bacteria and protozoa ( cop- 

 rophilic forms), many of these organisms die out in the process of 

 composting and are replaced by others which are characteristic of 

 the compost or of the soil. Among these, the thermophilic micro- 

 organisms, comprising various fungi, actinomycetes, and bacteria, 

 occupy a unique place. They develop in the composts after the tem- 

 perature has reached 50-60° C. Some of them are able to grow even 

 at 65-75° C, bringing about active decomposition of the organic con- 

 stituents of the manure. These organisms are quite distinct from 

 the typical soil population. This has bearing upon the various re- 

 ports that manure should be considered a source of bacteria for soil 

 inoculation. 



Conservation of Stable Manures 



A number of processes are utilized in the treatment of manures, 

 to conserve the nutrients and render the manures highly beneficial 



