Reduction of Chemical Fertilizers in Biochar Amended Soils.

Biochar is a carbon-enriched material obtained from the thermochemical conversion of biomass under oxygen-limited conditions. The use of biochar as a soil amendment has been proposed as a means to sequester carbon and improve soil quality. This study aims to explore whether biochar as soil amendment can reduce chemical fertilizer use in mollisol soils while preserving high crop yields. A laboratory experiment was conducted to screen the sorption capacities of a variety of biochars for nutrients such as ammonium and phosphate ions (NH₄⁺ and PO₄^3-). The adsorption mechanisms of two nutrient compounds on biochar were identified. Two biochars produced from wood wastes were found to simultaneously sorb NH₄⁺ and PO₄^3-, suggesting that the addition of biochar into soil can hold nutrients in soil, prevent their runoff or leaching, and thereby retain them so they are available to plants. A greenhouse study was conducted to investigate the effect of the combined use of biochar and fertilizer on radish yields. The biochar amendment rates and fertilizer application amounts were further assessed and optimized based on crop yields. A field trial was conducted in an Illinois corn field to demonstrate that biochar as a soil amendment can improve soil quality and increase crop yields. A synergetic effect was observed when biochar was combined with fertilizer application. This study clearly indicates that the addition of biochar into rich soils may reduce the use of chemical fertilizer and thereby minimize nutrient loading to aquatic environments.