DECOMPOSITION OF LAND APPLIED OILY FOOD WASTE AND ASSOCIATED CHANGES IN SOIL AGGREGATE STABILITY

Since traditional methods of disposing of oily food wastes have recent ly lost favor, there is a current search for alternatives. Field- and laboratory-scale experiments examined the decomposition of oily food w astes applied to agricultural lands to examine this disposal option an d potential agronomic benefits. Treatment rates of oily food waste equ ivalent to 3 to 11.3 g of C kg(-1) increased soil microbial biomass C in the field by up to five times control levels. Wet aggregate stabili ty also increased with waste addition and was maintained over the cour se of the growing season. Laboratory incubation studies examining the biodegradation of canola oil and oily food waste showed that the oily fraction of the waste was not rate limiting, and that both substrates degraded rapidly with initial decomposition half-lives of 40 to 45 h a nd 70 to 94 h for canola oil and waste treatments, respectively. The e xtents of mineralization over 4 wk were up to 83 and 40% for canola oi l and oily food waste, respectively, Similar to the field, increases i n aggregate stability were measured in the canola oil incubation. Exam ination of the biodegradation data indicates two substrate pools are b eing sequentially decomposed, and that the added substrate is not dire ctly responsible for improved structural properties. The longer lastin g binding abilities of microbial products and bodies are the major con tributing factors for the increased soil aggregation, It is concluded that the land application of oily food waste is agronomic ally benefic ial by increasing soil microbial activity, and in turn improving soil structure through increased aggregate stability.