Composting of Fish Waste with Wood By-products and Testing Compost Quality as a Soil Amendment: Experiences in the Patagonia Region of Argentina

Composting experiments of fish processing wastes and wood by-products were conducted in the Andean-Patagonian Region. Fish wastes were mixed with sawdust + wood shavings (3:l ratio by weight) with two replicates. Materials were mixed and placed in 220-liter PVC reactors. After 20 days, materials were remixed and reloaded in the reactors. Samples were taken at 20, 30, 40, 60, 80 and 100 day intervals and chemical analyses were made to assess predictors of compost stability. Thermophilic temperatures over 55°C were sustained long enough to satisfy the EPA requirements for pathogen reduction (72 hours). The decrease of NH4+-N, water soluble carbon and the ratio of water soluble carbon to total nitrogen appeared to be the best parameters for predicting compost stability. Mature compost (CMP) and an organic commercial product, Lombriquen (LQN) were incubated with an Andisol and a Xeric Mollisol at a rate o f 10g/kg for 16 weeks (20 to 30 percent soil moisture, 25°C) in order to estimate nitrogen and phosphorus release. Soils amended with LQN retained more P than CMP-amended soils (80 percent vs 60 percent of added Olsen-P in the Andisol and 50 vs 35 percent in the Xeric Mollisol). While N mineralization rates of LQN were variable (three to 11 percent of added total N), CMP showed constant rates for both types of soils (12 percent) and released more available N than LQN.