Application of biochar has been suggested to improve water- and fertilizer-retaining capacity of agricultural soil. Th e objective of this study was to evaluate the eff ects of bagasse charcoal (sugarcane [Saccharum offi cinarum L.] bagasse-derived biochar) on nitrate (NO3-) leaching from Shimajiri Maji soil, which has low waterand fertilizer-retaining capacity. Th e nitrate adsorption properties of bagasse charcoal formed at fi ve pyrolysis temperatures (400-800oC) 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 800oC. Nitrate adsorption by bagasse charcoal (formed at 800oC) 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 (800oC)-amended soils are aff ected 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 (800oC)-amended soils with diff erent 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 (800oC). We conclude that application of bagasse charcoal (800oC) 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-.
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