Regulation Measures Of Nitrogen Conversion Process On Purple Soil Study On The Fate Of Nitrogen Environment In Rice-wheat Rotation System

Nitrogen use efficiency of purple soil farmland in hilly area of Sichuan Basin is low.Nitrogen leaching by NO₃^-and ammonia volatilization loss are the important reasons for regional water,soil and gas quality degradation.In the past,a large number of studies have been carried out on the fate of nitrogen fertilizer,environmental impact and management measures in purple soil,but there is still a lack of targeted control measures based on the characteristics of nitrogen transformation in purple soil.Therefore,based on the understanding of the nitrogen conversion characteristics of purple soil,this study took Sichuan calcareous purple soil rice-wheat rotation system as the research object and formulated nitrogen conversion control measures（biological nitrification inhibitor MHPP,urease inhibitor NBPT,Biomass charcoal BC）,the experiment set a total of 9 treatments:（1）control group CK;（2）conventional fertilization group CF;（3）conventional fertilization+urease inhibitor NBPT;（4）conventional fertilization+biological nitrification inhibitor MHPP;（5）conventional fertilization+biomass charcoal BC;（6）conventional fertilization+urease inhibitor+biological nitrification inhibitor NBPT+MHPP;（7）conventional fertilization+urease inhibitor+biomass charcoal NBPT+BC;（8）Conventional fertilization+biological nitrification inhibitor+biomass charcoal MHPP+BC;（9）conventional fertilization+urease inhibitor+biological nitrification inhibitor+biomass charcoal NBPT+MHPP+BC.Through carrying out pot experiments,comprehensively using the static box method and continuous closed pumping method,etc.,to study the effects of nitrogen control measures on the fate of the nitrogen environment of the purple soil rice-wheat rotation system and the absorption and utilization rate of nitrogen fertilizer,including ammonia（NH₃）volatilization and oxidation Nitrogen（N₂O）emissions,nitrate nitrogen（NO₃^-）leaching,crop nitrogen uptake,etc.,in order to provide a reasonable scientific basis for improving the utilization rate of nitrogen fertilizer in purple soil and alleviating the pressure of natural environment.The main findings are as follows:（1）The proportion of nitrogen environmental fate in the calcareous purple soil-wheat system is:crop nitrogen uptake（52%）>N leaching loss（24%）>soil residual nitrogen（16%）>NH₃ volatilization loss（6%）>N₂O emissions（2%）.The single application or combined application of regulation measures（biological nitrification inhibitors,urease inhibitors and biomass charcoal）in the nitrogen conversion process can increase the nitrogen uptake of the above-ground parts of wheat crops（5.03～56.18%）;single application of urease inhibitor treatment and Three kinds of control measures combined application treatment can increase N leaching loss（5.07～8.33%）,other nitrogen control measures can reduce nitrogen leaching loss in soil solution（6.37～34.89%）;single application of biological nitrification inhibitor increases NH₃ The risk of volatilization loss（7.84%）,the remaining nitrogen control measures are effective to reduce NH₃ volatilization loss（16.09～35.45%）;the single application of biological nitrification inhibitor treatment increases the soil inorganic nitrogen residue by 11.37%,and the remaining nitrogen control measures are effectively reduced Inorganic nitrogen residual content（11.28～17.15%）;the control measures in the nitrogen conversion process significantly reduced N₂O emissions（16.07～35.41%）（p<0.05）.（2）Single application or combined application of regulation measures（biological nitrification inhibitor,urease inhibitor and biomass charcoal）in calcareous purple soil-wheat system,except for combined application of urease inhibitor and biological nitrification inhibitor There is a 7.13%yield increase effect for wheat,and the remaining control measures have no significant yield increase effect（p>0.05）.（3）The proportion of nitrogen environment fate in the calcareous purple soil-rice system is:crop nitrogen uptake（51.66%）>N leaching loss（20.22%）>NH₃ volatilization loss（15.66%）>soil residual nitrogen（12.45%）>N₂O emissions（0.01%）.The single application or combined application of regulation measures（biological nitrification inhibitors,urease inhibitors and biomass charcoal）in the nitrogen conversion process can increase the nitrogen uptake of the above-ground parts of rice crops（2.80-18.68%）;urease inhibitor treatment and biomass The combined application of carbon treatment can increase the N leaching loss by 0.54%,and other nitrogen control measures can reduce the nitrogen leaching loss in soil solutions（1.25～25.79%）;the application of a biological nitrification inhibitor alone increases the risk of NH₃ volatilization loss（16.92%）,the remaining nitrogen control measures are effective in reducing NH₃volatilization losses（16.12～24.71%）;nitrogen control measures all increase the soil inorganic nitrogen residual content（2.81～18.68%）;each treatment of the nitrogen conversion process control measures significantly reduces N₂O emissions（16.27～35.71%）（p<0.05）.（4）The single application or combined application of regulation measures（biological nitrification inhibitors,urease inhibitors and biomass charcoal）in the calcareous purple soil-rice system can increase the yield of rice（2.47～10.31%）,of which The combined application of biological nitrification inhibitor,biomass charcoal and urease inhibitor can increase the yield of rice by 10.31%.To sum up,when adjusting nitrogen in calcareous purple soil,appropriate control measures should be selected according to the purpose of adjustment,and the factors such as environment and crop yield should be integrated.It is recommended to use urease inhibitor and biological nitrification inhibitor in the calcareous purple wheat system,and biochar,urease inhibitor and biological nitrification inhibitor in the calcareous purple rice system,it can reduce the loss of soil nitrogen,improve the utilization rate of nitrogen and relieve the pressure of nitrogen loss on the natural environment.