Hadas, A., Institute of Soils and Water, ARO, The Volcani Center, Bet Dagan, 50250, Israel
Kautsky, L., Institute of Soils and Water, ARO, The Volcani Center, Bet Dagan, 50250, Israel

Plant nutrition in organic farming is based entirely on decomposition of organic materials, and release of excess N superfluous to the microbial population. Feather meal (FM), a by-product of the poultry processing industry, which contains 15% N as non-soluble keratin, is a potential organic N fertilizer. The objective of this study was to determine the rate of N mineralization and changes in microbial activity following the application of FM to soil. Soils were incubated with FM for 8 weeks at 30°C and optimal water content, and analyzed periodically for inorganic N, rate of CO2 evolution, counts of microbial populations, and activity of dehydrogenase and protease. Approximately 45, 55 and 65% of fertilizer N were released after 1, 2, and 8 weeks, respectively. Total number of bacteria increased due to the addition of FM after only 1 d, with a second pulse obtained at 14 d. Dehydrogenase activity followed a similar response cycling. Cellulose hydrolyzing bacteria and proteolitic bacteria increased later, between 5 and 21 d, probably due to secondary microbial decay products. Microbial biomass N at 5 to 7 d accounted for 10 to 14% of total FM-N, therefore the slow release of N from FM was due in part to its resistance to decomposition and in part to microbial biomass build-up and secondary decomposition. © 1994 Kluwer Academic Publishers.