Effects Of Combined Application Of Biochar,Urease Inhibitor And Urea On Nitrogen Utilization And Soil Quality In Winter Wheat And Summer Maize

Lower soil fertility is one of the main factors restricting the sustainable development of agricultural production in arid areas of loess plateau.Excessive use of fertilizer has caused problems such as low utilization of nitrogen fertilizer,energy waste and environmental pollution.More attention has been paid to the optimization of cultivation measures,fertilization managent and the improvement of nitrogen fertilizer utilization.Urease inhibitors increase the retention time of nitrogen fertilizer in soil by delaying urea hydrolysis.Urease inhibitor is an effective means to improve nitrogen utilization and reduce nitrogen resource loss,but the effect of urease inhibitor in farmland is easily influenced by the activity of the product itself and soil environment,and its application effect is unstable.In addition,biochar has unique physico-chemical properties,such as large surface area and adsorption capacity,and high porosity.It has great potential to improve soil quality,increase crop yield and reduce ammonia volatilization loss.However,the research and application of biochar and urease inhibitors in China is still in its infancy,and the effects of the combination of biochar and urease on soil nitrogen use and soil quality in upland arid agricultural areas need further study.In this experiment,the yield,nitrogen utilization efficiency,soil fertility and ammonia volatilization under the application of biochar,urease inhibitor and nitrogen fertilizer were studied in a field plot of summer maize-winter wheat crop rotation system.Fertilizer treatment was dominated by 5 nitrogen fertilizer rates(N0,N75,N150,N225and N300 kg N ha^-1);urease inhibitor（NBPT）with 0%and 2%NBPT;and biochar with 0%and 7.5 t C ha^-1,were applied individually or in combination.The main results were as follows:（1）Nitrogen application significantly increased maize and wheat grain yield（P<0.05）.With the increase in nitrogen application,grain yield showed a trend of first increasing and then decreasing,both peaking at N225.Biochar application significantly increased grain yield（P<0.05）.Among them,maize yield increased by4.38%and wheat grain yield increased by 2.42%.Urease inhibitor（NBPT）increased seed yield.（2）Nitrogen application significantly affected plant nitrogen uptake accumulation and apparent nitrogen fertilizer utilization.Plant nitrogen uptake increased with nitrogen application,while the apparent recovery of nitrogen fertilizer decreased with the increase of nitrogen application rate.（P<0.05）.Urease inhibitor（NBPT）increased the apparent nitrogen recovery of maize.Biochar application significantly increased the apparent nitrogen recovery of maize and wheat fertilizer（P<0.05）by 25.78%and13.57%,respectively.（3）Soil ammonia volatilization accumulation reached 11.53 to 13.01 kg N ha^-1in maize and 15.70 to 16.81 kg Nha^-1in wheat during whole growth,and N300 treatment showed a significant increase in soil ammonia volatilization accumulation（P<0.05）compared to no nitrogen application（N0）.Enzyme inhibitors（NBPT）significantly reduced soil ammonia volatilization accumulation by 4.14%in wheat（P<0.05）,and biochar decreased soil ammonia volatilization accumulation in wheat and maize growth seasons（P<0.05）.（4）The application of biochar can improve the physical properties of 0-10 cm of soil,increase large aggregates,reduce bulk weight and increase porosity.Nitrogen application and biochar application had a significant effect on soil microbial biomass carbon and soil microbial biomass nitrogen（P<0.05）.The application of biochar also contributed to the improvement of nutrients in the 0-10cm ploughing layer,with the most significant effect on organic carbon.（5）Urease activity,soil microbial biomass carbon,total phosphorus,available potassium,total nitrogen and p H are representative indicators of soil fertility（MDS）.Application of biochar contributes to soil fertility（SQI）.N225 and N300 had the highest SQI with biochar treatment.To sum up,combined application of biochar could not only ensure the yield of summer maize and winter wheat,but also reduce ammonia volatilization and improve the effective fertility of topsoil.Enzyme inhibitors（NBPT）had more effects of enhanced yiled and mitigation of ammonia volatilization on wheat than mazie.