| In this study, an incubation and laboratory column experiments were conducted to assess the effects of biochar（corn-stalk biochar, rice-hull biochar and larch biochar） at four rates of application（0.6%,1.2%,3.6%,6%） on p H, EC, volume, inorganic nitrogen（NH4+-N and NO3--N）concentration in leaching solution, inorganic nitrogen leaching amount in black soil as well as adsorption and desorption of inorganic nitrogen in black soil. And this study also discussed the adsorption and desorption of nitrogen of soil clay minerals with biochars（complex）.The results showed that: 1) Biochar application increased the p H and EC of soil leaching solution, and they were in direct proportion to the application rates of biochar. The effect of different biochars on p H was: corn-stalk biochar > rice-hull biochar > larch biochar, and the effects of different biochars on EC was: rice-hull biochar > larch biochar> corn-stalk biochar. Biochar application reduced the volume of soil leaching solution, which was inverse proportion to the application rates of biochar, significantly lower than that of CK（P<0.05）. 2) Biochar application reduced the NH4+-N concentration in leaching solution and the NH4+-N leaching amount in soil, and the effects of biochar was: corn-stalk biochar > rice-hull biochar > larch biochar. The lowest concentration and the leaching amount of NH4+-N was found at a biochar rate of 3.6%.Biochar application reduced the NO3--N concentration in leaching solution and the NO3--N leaching amount in soil, and the effects of biochar was: corn-stalk biochar > rice-hull biochar > larch biochar. The concentration and the leaching amount of NO3--N was the lowest when the corn-stalk biochar at the rate of 1.2%, the rice-hull biochar and larch biochar at the rate of 3.6%. 3) Biochar applications increased NH4+-N adsorption, with the highest adsorption capacity occurred in soil added with 3.6% biochar. Of three biochars, corn-stalk biochar had the highest NH4+-N adsorption capacity, which was 4.037 mg/g, whereas larch biochar had the lowest NO3--N adsorption, with only 2.021 mg/g. Applications of biochars reduced the desorption rates of NH4+-N from soil. The lowest desorption was found at a biochar rate of 3.6%. On the contrary, corn-stalk biochar had the lowest NH4+-N desorption while larch biochar displayed the highest desorption. The adsorption ability of NH4+-N by biochars was: corn-stalk biochars>rice-hull biochar > larch biochar, but the desorption was opposite. The isothermal adsorption of NH4+-N on soil amended with biochars could be well described by Langmuir isothermal equation.Biochar applications increased NO3--N adsorption, with the highest adsorption capacity occurred in soil added with 1.2% and 3.6% corn-stalk as well as 3.6% rice-hull biochar and larch biochar. Of three biochars, corn-stalk biochar had the highest NO3--N adsorption capacity, which was 0.929 mg/g, whereas larch biochar had the lowest NO3--N adsorption, with only 0.578 mg/g. Applications of biochars reduced the desorption rates of NO3--N from soil. The lowest desorption was found at a biochar rate of 3.6%. On the contrary, corn-stalk biochar had the lowest NO3--N desorption while larch biochar displayed the highest desorption. The adsorption ability of NO3--N by biochars was: corn-stalk biochars>rice-hull biochar > larch biochar, but the desorption was opposite. The isothermal adsorption of NO3--N on soil amended with biochars could be well described by Langmuir isothermal equation.4) Biochar- montmorillonite complex, biochar- vermiculite complex and biochar- illite complex showed well adsorption of NH4+-N. The three kinds of complexes had the highest adsorption capacity of NH4+-N added with 3.6% biochar. Of three complexes, biocharmontmorillonite complex had the highest NH4+-N adsorption capacity, whereas biochar- illite complex had the lowest NH4+-N adsorption. The adsorptivity of NH4+-N of corn-stalk biocharmontmorillonite complex, corn-stalk biochar- vermiculite complex and corn-stalk biochar- illite complex were higher than other complexes, which were 0.648 mg/g, 0.447 mg/g and 0.408 mg/g respectively. The isothermal adsorption of NH4+-N on soil clay minerals with biochars（complex） could be well described by Langmuir isothermal equation. Moreover, the lowest desorption was found at biochar- montmorillonite complex, while biochar- illite complex displayed the highest desorption.Biochar- montmorillonite complex, biochar- vermiculite complex and biochar- illite complex showed well adsorption of NO3--N. The three kinds of complexes had the highest adsorption capacity of NO3--N added with 3.6% biochar. Of three complexes, biocharmontmorillonite complex had the highest NO3--N adsorption capacity, whereas biochar- illite complex had the lowest NO3--N adsorption. The adsorptivity of NO3--N of corn-stalk biocharmontmorillonite complex, corn-stalk biochar- vermiculite complex and corn-stalk biochar- illite complex were higher than other complexes, which were 0.432 mg/g, 0.426 mg/g and 0.390 mg/g respectively. The isothermal adsorption of NO3--N on soil clay minerals with biochars（complex） could be well described by Langmuir isothermal equation. Moreover, the lowest desorption was found at biochar- montmorillonite complex, while biochar- illite complex displayed the highest desorption. |
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