Effects of Biochar Treatment of Municipal Biosolids and Horse Manure on Quality of Runoff from Fescue Plots

Abstract

<abstract> Land-applied horse manure and municipal biosolids can increase nutrient and bacteria concentrations in runoff. Biochar has been demonstrated to have beneficial impacts on nutrient retention and runoff quality when used to treat other land-applied organic soil amendments (e.g., poultry manure). The objective of this study was to evaluate the effects of biochar addition to horse manure and municipal biosolids on runoff concentrations of nutrients and fecal coliforms. Biochar was added at 5% to 8% (wet basis) to horse manure and biosolids that were applied to 2.4 m x 6.1 m fescue plots followed by application of simulated rainfall (102 mm h^-1). Analysis of runoff samples indicated that soil hydraulic characteristics, as reflected in the runoff curve number (CN), were a significant covariate for some analytical parameters. Analysis of covariance indicated that biochar addition decreased runoff concentrations of total Kjeldahl nitrogen (TKN) and ammonia nitrogen (NH₃-N) when added to municipal biosolids, with all effects more prominent at higher CN values. When added to horse manure, biochar decreased runoff concentrations of NH₃-N, total suspended solids, and fecal coliforms. Although runoff concentrations of total P and TKN increased with CN, there was no significant biochar effect on these parameters when added to horse manure. The findings indicate potential for biochar addition to improve runoff quality when added to these organic amendments, but the effects may be dependent on the receiving soil‘s runoff production characteristics.