Effects Of Biochar On The Behavior Of Fertilizer N In Soil-wheat Systems

In the black soil region of northeast China,soil degradation is serious due to frequent ploughing,surface exposure,high intensity output and lack of organic inputs.The decrease of soil organic matter is accompanied by the decrease of soil fertility,especially the decrease of nitrogen regulation ability,resulting in the decrease of soil nitrogen supply capacity and nitrogen use efficiency,which has become the bottleneck restricting the sustainable development of grain production in northeast China.At the same time,the loss of nitrogen also causes serious environmental pollution.Therefore,the research on the transformation process and regulation technology of soil nitrogen in main dryland in the black soil region can not only increase the yield benefit of crops,reduce the cost,guarantee the national food security,but also improve the utilization efficiency of nitrogen fertilizer,boost the strategy of "storing grain in the ground",and promote the sustainable development of agriculture in the black soil region of northeast China.Known as "black gold",biochar with complex porous structure and huge specific surface area can be used as nutrient carrier,which can effectively alleviate the release rate of fertilizer nutrients in soil,reduce the loss of nutrient leaching and washing,thus improving the utilization rate of fertilizer and playing a role of slow release and efficiency enhancement.Based on this,in this study,thin layer black soil and white clay soil in the black soil region of northeast China were selected as the research object.Under the reduced application condition,greenhouse pot cultivation and 15N stable isotope tracer technology were used to apply biochar with ammonium sulfate fertilizer(low N,high N and medium N).By analyzing the effects of biochar on soil physical and chemical properties,residual nitrogen in soil and plant nitrogen accumulation,the effects of biochar on soil N supply capacity and soil physical and chemical properties were systematically studied.Effects of N residue in soil from biochar fertilizer N,N absorption and N supply capacity of plants;The effect of biochar on the distribution and whereabouts of fertilizer N in soil-crop system is expected to provide theoretical basis for further regulation of soil nitrogen cycle and supply in black soil area and rational use of biochar and nitrogen fertilizer.The main results are as follows:1.Biochar application alone and biochar combined with nitrogen fertilizer significantly increased soil pH value,which increased by 3.0%-5.6%in white clay soil and 2.6%-4.5%in black soil,respectively.Biochar,single application of nitrogen fertilizer and biochar combined application of nitrogen fertilizer had significant effects on soil pH.2.In each growth stage of wheat,the biochar treatments could significantly increase the content of organic matter in soil,and the increase of organic matter in white clay and black soil was 7.9%-12.1%and 11.8%-15.9%,respectively,at maturity stage.3.Compared with nitrogen application alone,biochar combined with nitrogen application could reduce the inorganic nitrogen residue in soil from fertilizer nitrogen,and biochar had a significant effect on high nitrogen application.4.In the soil-crop system,biochar combined with nitrogen fertilizer significantly improved the efficiency of plant nitrogen use,and reduced the residual inorganic nitrogen from fertilizer nitrogen in soil.5.The fertilizer N residual rate in black soil was significantly higher than that in white clay soil.The difference of nitrogen use efficiency between black soil and white clay soil increased first and then decreased.