Co-application of Papermill Sludge and Wood Ash Improves Forage Crop Yield and Soil Health in a Greenhouse Trial

Application rates of papermill residual (PMR) in Ontario, Canada, are regulated to a wet weightmaximum of 20 Mg ha−1 yr−1 with the actual rate determined by the concentrations of plant available nitrogen, phosphorous, potassium and 10 regulated metals in the materials and receiving soils. Previous studies report improvements in crop yield and soil properties following PMR application but generally at rates far exceeding 20 Mg ha−1 yr−1 and after years of repeated application. We investigated whether application of PMR at operational rates could enhance the forage crop yield and improve soil health in three locally sourced agricultural soils in a greenhouse experiment. When papermill sludge (PPMS) was incorporated into the soils, forage yields were comparable to, or greater than, those achieved with mineral fertilizer in two of the three soils. The largest yield increases occurred when PPMS was applied in combination with wood ash. Application of PPMS alone did not produce statistically significant changes in soil health scores, but scores improved by up to ten points when PPMS and wood ash were applied together. When PMR is available locally, land application, particularly when PPMS is applied with wood ash, can reduce dependence on conventional amendments to improve agricultural outcomes.