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 sugarcane bagasse-derived biochar on nitrate leaching from Shimajiri Maji soil, which has low water- and fertilizer-retaining capacity. The nitrate adsorption properties of biochar formed at five pyrolysis temperatures (400-800 degrees) were investigated to select the most suitable biochar for nitrate adsorption. Nitrate was able to adsorb on to the biochar formed at pyrolysis temperatures of 700-800 degrees. Nitrate adsorption by biochar (formed at 800 degrees) 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 KNO3 solution. Measurements suggested that the saturated and unsaturated hydraulic conductivity of biochar (800 degrees)-amended soils are affected by changes in soil tortuosity and porosity and the presence of meso- and micropores in the biochar, which did not contribute to soil water transfer. In nitrate leaching studies using biochar (800 degrees)-amended soils with different biochar contents (0-10 wt%), the maximum concentration of nitrate in effluents from biochar-amended soil columns was approximately 5% less than that from a non-amended soil column because of nitrate adsorption by biochar (800 degrees). We conclude that application of biochar (800 degrees) to the soil will increase the residence time of nitrate in the root zone of crops and provide greater opportunity for crops to absorb nitrate.