Impacts of Biochar Aging and Soil Type on Soil Nitrogen Dynamics.

Interactions between soil type, biochar type, and biochar aging may influence N cycling in soils. To gain a better understanding of biochar impacts on N mineralization and nitrification (gross N transformation process), an ¹⁵N tracer study in combination of numerical data analysis has been employed using fresh and laboratory-aged fast pyrolysis biochars and three soil types (sandy loam, silt loam, and clay loam). Soils were mixed with biochar (1% w/w) and sub-samples were then incubated with N-fertilizer (¹⁵NH₄Cl; at the rate of 170 N lbs/acre) for 0, 3, 7, 14, 35, 63, and 98 days. Moisture content was maintained at field capacity during the incubation. Measurements of ammonium (NH₄⁺) and nitrate (NO₃^-) concentrations and ¹⁵N:¹⁴N ratios will be analyzed to assess the impact of biochar on soil gross N transformation and nitrification and mineralization rates. The use of the ¹⁵N fertilizer will allow us to distinguish between fertilizer and soil organic matter sources of NH₄⁺ and NO₃^-. A detailed understanding of biochar effects on N cycling in soils is needed to more accurately calibrate and if necessary revise the new biochar module in the APSIM cropping systems model to better predict biochar impact on soil N bio-availability and N leaching.