Feather meal, a semi-slow-release nitrogen fertilizer for organic farming

Abstract

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.