An Evaluation of Soil Nutrient Status Following the Application of (i) Co-composted MSW and Sewage Sludge and (ii) Greenwaste to Maize

This paper describes the some of the results of a two experiment conducted to investigate the agronomy and environmental impact associated with the use of (i) co-composted municipal solid waste and sewage sludge (MSW) and (ii) composted greenwaste (GW) on forage maize. The experiment was conducted on a silty loam soil in South West England. In 1994 MSW and GW treatments of 15, 30 and 50 t ha-1 were compared with fertilizer and an untreated control. All treatments were replicated three times. The composts used were significantly different with respect to pH, loss-on-ignition, total potassium and calcium, but not mineral nitrogen or C:N ratio. No significant differences in soil nutrient status were observed between compost types or rates after drilling. The inorganic fertilizer treatment which showed significantly higher levels of mineral nitrogen but not P or K. Patterns of extractable nitrate-N recorded during the summer 1994 were very variable, and only the fertilizer treatment was significantly different from the compost or control treatments, and then not on every occasion. Post-harvest leaching on nitrate-N again showed no consistent pattern between compost types or application rates, while losses from the fertilized plots exceeded all other treatments. It is concluded that at the rates used in this experiment, the nutrients contained in composted MSW and GW can be considered environmentally benign.