Effects Of Nitrification Inhibitor On Soil Nitrogen Transformation Process And Nitrogen Use Efficiency Of Maize Under Shallow Buried Drip Irrigation

Filmless shallow buried drip irrigation technology has become a large-scale application of water-saving and water-fertilizer integration technology in arid and semi-arid areas of Inner Mongolia.However,the research on shallow buried drip irrigation technology during the’13th Five-Year Plan’period shows that the emission of greenhouse gases such as N₂O increases under the integration of water and fertilizer in shallow buried drip irrigation,resulting in an increase in the loss of active nitrogen and the risk of environmental pollution.There is still great potential for reducing losses and reducing nitrogen efficiency.In order to solve this problem,this study set up five fertilization methods:no fertilization（N0）,conventional fertilization（CF）,20%reduction of nitrogen fertilizer（80%CF）,conventional fertilization+nitrification inhibitor（CF+DCD）,20%reduction of nitrogen fertilizer+nitrification inhibitor（80%CF+DCD）under the water and fertilizer integration mode of shallow buried drip irrigation.By dynamically measuring soil nitrogen forms,soil nitrification and denitrification key enzyme activities and nitrogen nutrition status of maize plants,the effects of reducing nitrogen fertilizer and adding nitrification inhibitor on nitrogen process and nitrogen absorption and utilization of maize were analyzed.The main results are as follows:（1）Compared with CF,80%CF+DCD decreased soil ammonia monooxygenase activity by 18.36%,nitrate nitrogen content by 31.88%,ammonium nitrogen content by40.14%,and nitrate nitrogen residue by 49.42%in 0-90 cm soil layer,Thus reducing the risk of nitrate leaching and N₂O emission loss.（2）The addition of nitrification inhibitors at 20%of nitrogen fertilizer significantly increased the absorption and utilization of nitrogen in maize.The nitrogen accumulation of 80%CF+DCD was 4.38%higher than that of CF,and the nitrogen accumulation before anthesis was significantly increased by 3.87%.The nitrogen use efficiency,nitrogen uptake efficiency and nitrogen physiological efficiency were increased by 35.73%,34.21%and 10.89%,respectively.The partial productivity and contribution rate of nitrogen fertilizer increased by 27.13%and 6.72%,respectively.It indicated that the addition of nitrification inhibitors significantly improved the soil nitrogen supply,and significantly improved the nitrogen use efficiency by increasing the nitrogen uptake of maize.（3）Reducing nitrogen fertilizer by 20%on the basis of conventional fertilization will not cause maize yield reduction,but adding nitrification inhibitors on the basis of reducing nitrogen fertilizer by 20%can significantly increase maize yield by increasing1000-grain weight.The 1000-grain weight of 80%CF+DCD was 3.05%higher than that of CF.The yield increased by 1.20%.In summary,under the condition of shallow drip irrigation with 20%reduction of nitrogen fertilizer,the addition of nitrification inhibitors delayed the conversion of NH₄⁺-N to NO₃^--N after urea hydrolysis by inhibiting soil ammonia monooxygenase activity,significantly increased soil ammonium nitrogen content,and reduced soil nitrate nitrogen content and nitrogen residue,thus reducing the risk of nitrate leaching and N₂O emission loss.The higher NH₄⁺-N level in the soil promoted nitrogen absorption and biomass accumulation of maize,and significantly increased maize yield and nitrogen use efficiency by improving grain development.