314 



Manures, Composts, Green Manures 



Table 70. Chemical Composition ov Plant Residues, Manures, 

 AND Soil Humus (from Pic-hard) 



Per cent of total organic matter. 



frequent enough for proper aeration, which favors development of 

 aerobic fungi, actinomycetes, and bacteria. The moisture content 

 of the compost must be adjusted to 75-80 per cent. If excess water 

 is added, anaerobic conditions, which will retard decomposition, are 

 created. With insufficient water, especially in loose, open heaps, 

 nitrogen losses may result, and an inferior product is obtained. 



Figure 122 gives the relative composition of artificial manure and 

 of the original plant material from which it was prepared. Oat straw 

 was allowed to decompose for 273 days at 37°C in the presence of 

 added inorganic nutrient salts. In that time, the cellulose disap- 

 peared almost completely, the hemicelluloses and fats were markedly 

 reduced, the lignin increased appreciably in relation to the other 

 constituents, and the relative amounts of ash and protein increased 

 to an even larger extent. The increase in the ash content is due to 

 its gradual accumulation, resulting from destruction of the organic 

 constituents. The increase in protein content is relatively greater 

 than the increase in ash; this is due both to the relative accumulation 

 of the protein parallel to the destruction of the carbohydrates and 

 to the synthesis of microbial proteins from the inorganic nitrogen 

 added to the compost. The lower the original nitrogen content of 

 the plant material used in the preparation of the compost, the greater 



