Utilization of plant residues for the production of artificial manures

Several artificial manures were prepared from organic residues by the composting process. At various intervals during decomposition, samples of the composts were analyzed for moisture, ash, ammonia nitrate, total nitrogen, pH, and approximate chemical composition. The temperature of each compost was recorded at frequent intervals and the dry weight of the organic material lost during decomposition was determined. The quality of the artificial manures produced was studied by greenhouse and field tests, which were supplemented by laboratory nitrification and fungus culture tests. The results are summarized as follows: 1. The fatty and waxy substances, water-soluble organic matter hemicelluloses, and cellulose underwent extensive decomposition in all the composts. 2. The extent of the lignin decomposition depended greatly upon the chemical nature of the plant materials used. The lignins in straw and cornstalks decomposed only slightly, whereas those in timothy hay, clover hay, and cow manure showed great decomposition. 3. The crude protein increased greatly in the oat straw + inorganic salts and the cornstalks + inorganic composts and slightly in the oat straw + clover hay compost. It decreased slightly in cow manure and lowmoor peat + timothy hay composts and to a considerable extent in the leaves + timothy hay compost. 4. For every 1,OOO pounds of organic residue used for composting, approximately 1 ton of artificial manure was produced. 5. The greenhouse and field studies demonstrated the production from cornstalks of a high quality artificial manure comparable to composted cow manure within a period of 3 months. Good quality products were prepared within 4 to 6 months from cereal straw. Resistant materials, such as salt-grass hay and woody residues, required much longer periods for proper decomposition. Tree and shrub trimmings and other woody materials should not be mixed with ordinary plant refuse because of the slowness with which they decompose. Such products should be built into a special manure pile and be allowed to decompose for a longer time. Composts from peat and leaves should be considered only as soil conditioners. They will, however, make high quality manures if reinforced with inorganic fertilizer. The residual effect of the composts produced from cow manure, cornstalks, and cereal straw was much greater than that of inorganic fertilizer. 6. Nitrification and fungus culture tests confirmed the results of the greenhouse and field tests.