Nutrient Limitations to Biochar Mineralization.

The by-product of energy producing pyrolysis, or biochar, is a potential source of carbon (C) sequestration and a soil amendment that may improve soil chemical and physical properties. The impact of biochars on soil C, nutrient cycling, and soil or water quality is still not well understood. Previous studies with biochar made from the wood of Amazonian successional tree species showed that mineralization was influenced by the type of wood used as feedstock and temperature of formation. More interestingly, the data indicated that after 100 days a biochar + soil mixture was mineralizing less C than the soil alone. Either the biochar was protecting soil carbon or inhibiting native soil C mineralization via nutrient limitations. This study addresses the latter hypothesis to explain those results. The objective of this study is to determine if soil texture and nutrient condition would affect C mineralization of biochar + soil mixtures.  The biochar + soil mixtures chosen were known to have a 10-fold difference in C mineralization. Fertilization treatments of N, P and N+P were added to sandy and clayey textured soils. Initial results show mineralization rate is affected by biochar and soil texture and fertilization does not impact mineralization. Carbon mineralization was found to be almost doubled due to biochar in the soil.