Nitrogen Dynamics Following Field Application of Biochar in a Temperate North American Maize-Based Production System.

Biochar additions to tropical soils have been shown to reduce N leaching and increase N use efficiency. However, No studies exist verifying reduced N leaching in field experiments on temperate agricultural soils or identifying the mechanism for N retention. Biochar derived from maize stover was applied to a maize cropping system in central New York State at rates of 0, 1, 3, 12, and 30 t ha^-1 in 2007. Secondary N fertilizer was added at 100, 90, 70, and 50% of the recommended rate (108 kg N ha^-1). Nitrogen fertilizer enriched with ¹⁵N was applied in 2009 to the 0 and 12 tha-1 of biochar at 100 and 50 % secondary N application. Maize yield and plant N uptake did not change with biochar additions (p>0.05; n=3). Less N (by 82%; p<0.05) was lost after biochar application through leaching only at 100% N fertilization. The reason for an observed 140% greater retention of applied ¹⁵N in the topsoil may have been the incorporation of added 15N into microbial biomass which increased approximately three-fold which warrants further research. The low leaching of applied fertilizer ¹⁵N (0.42% of applied N; p<0.05) and comparatively high recovery of applied ¹⁵N in the soil (39%) after biochar additions after one cropping season may also indicate greater overall N retention through lower gaseous or erosion N losses with biochar. Addition of biochar to fertile soil in a temperate climate did not improve crop growth or N use efficiency, but increased retention of fertilizer N in the topsoil.