DETERMINING OPTIMAL MATURITY OF COMPOST USED FOR LAND APPLICATION

A stable compost is needed in plant growth media. However, when compos t is land applied, its effect is through the initiation and accelerati on of microbial processes leading to the production of soil stabilizin g agents. It was proposed that there is an optimum degree of maturity of compost used for land application, a degree characterized by the re duction of the labile organic matter to a point when the material is r elatively stable yet is still active enough to support an increased mi crobial activity in the soil. The effect of composting time on the eff iciency of municipal solid waste compost (MSWC) to improve soil struct ural properties, evaluated through laboratory indexes, is presented in this work. MSWC was sampled immediately following 24 hours precompost ing in a Dano drum. Samples were taken throughout 60 days of windrow c omposting. The compost samples were mixed with a structure-impaired lo ess soil and incubated aerobically for 21 days. Hydraulic conductivity and residual turbidity, a measure of microaggregate stability, were m easured in solutions of two SAR levels, five and 20. Compost applicati on had a positive effect on these soil structural properties. The opti mal activity was obtained for the compost sampled following seven to 1 4 days of windrow composting. Polysaccharide concentrations also follo wed a similar optimum curve. The peak concentration was found followin g 14 to 30 days old compost application. The determination of the opti mal maturity of composted municipal solid wastes is essential toward a n efficient utilization of the compost, toward satisfaction of environ mental constraints and for a cost-efficient operation of composting pl ants. The present preliminary study calls for more research in this fi eld.