Biochar Influences On Nitrogen Leaching and Uptake Using 15N in a Maize Cropping System in the Northeastern U.S.

Biochar additions to tropical soils have been shown to reduce nitrogen leaching through increased adsorption capacity and greater fertilizer use efficiency. Few studies exist documenting this trend in temperate agricultural soils. To what extent the application rate of biochar has on fertilizer use efficiency is also not known. Biochar derived from maize stover under slow pyrolysis was applied to a maize cropping system at rates of 0, 3, 12, and 30 t ha^-1 in 2007. Nitrogen was applied at 12.35 kg N ha^-1 at planting and at 107.61 kg N ha^-1 six weeks after planting. The second application of N was applied at 100, 90, 70, and 50% of the maximum rate for each biochar application rate. Labeled isotopic ¹⁵N was applied for the 2009 season at 1 kg ¹⁵N ha^-1 for the treatment combinations of 0 and 12 t ha^-1 of biochar and 100 and 50% secondary N application. Free-draining lysimeters were installed at 60cm in these same treatments for the 2009 growing season to collect lechate. Initial results from the 2008 growing season indicate the rate of biochar does not significantly affect maize grain or biomass yield. There were no significant differences in yield between the plots receiving biochar and those not receiving biochar for any of the fertilization rates. Increased cation exchange capacity is a proposed mechanism for improved reduced leaching and improved fertilizer use efficiency documented with biochar additions. Charge development of in biochar is the result of surface oxidation of the biochar particles. The insignificant differences found between the treatments might be due to insufficient time for surface oxidation and change development to occur. Significant results might bee seen in the 2009 cropping season due to increased time for these processes to occur.