Influence of Sugarcane Bagasse-derived Biochar Application on Nitrate Leaching in Calcaric Dark Red Soil

Application of biochar has been suggested to improve water- and fertilizer-retaining capacity of agricultural soil. The objective of this study was to evaluate the effects of bagasse charcoal (sugarcane [Saccharum officinarum L.] bagasse-derived biochar) on nitrate (NO3-) leaching from Shimajiri Maji soil, which has low waterand fertilizer-retaining capacity. The nitrate adsorption properties of bagasse charcoal formed at five pyrolysis temperatures (400-800 C) were investigated to select the most suitable bagasse charcoal for NO3- adsorption. Nitrate was able to adsorb onto the bagasse charcoal formed at pyrolysis temperatures of 700 to 800 degrees C. Nitrate adsorption by bagasse charcoal (formed at 800 degrees C) that passed through a 2-mm sieve was in a state of nonequilibrium even at 20 h after the addition of 20 mg N L-1 KNO3 solution. Measurements suggested that the saturated and unsaturated hydraulic conductivity of bagasse charcoal (800 degrees C)-amended soils are affected by changes in soil tortuosity and porosity and the presence of meso-and micropores in the bagasse charcoal, which did not contribute to soil water transfer. In NO3- leaching studies using bagasse charcoal (800 degrees C)-amended soils with different charcoal contents (0-10% [w/w]), the maximum concentration of NO3- in effl uents from bagasse charcoal-amended soil columns was approximately 5% less than that from a nonamended soil column because of NO3- adsorption by bagasse charcoal (800 degrees C). We conclude that application of bagasse charcoal (800 degrees C) to the soil will increase the residence time of NO3- in the root zone of crops and provide greater opportunity for crops to absorb NO3 (-).