Effect Of Combined Application Of Biochar And Nitrification Inhibitor On Emission Reduction Of Vegetable Soil And Its Microbiological Mechanism

Nitrous oxide and nitric oxide play an important role in the nitrogen cycle.As two active greenhouse gases,nitrous oxide and nitric oxide can directly or indirectly affect the process of global warming.Due to the characteristics of high intensive planting and large amount of fertilizer application in vegetable fields,farmland ecosystem has become the main source of atmospheric N₂O and NO emissions.In this study,the content and intensity of soil inorganic nitrogen,the emission law of N₂O and NO and the gene abundance of soil nitrogen cycle under the combined application of biochar and nitrification inhibitor were studied through indoor culture experiment,in order to clarify the regulation of biochar and nitrification inhibitor on soil digestion process and the emission reduction effect of N₂O and NO in hot area.Four treatments were set up in this experiment:single application of nitrogen fertilizer(N),with biochar(N+Bc),nitrification inhibitor with nitrogen fertilizer(N+Ni)and nitrification inhibitor with nitrogen fertilizer with biochar and nitrification inhibitor(N+Bc+Ni).The main results are as follows:(1)The addition of biochar can reduce the NH₄⁺-N strength by 33%,and the addition of nitrification inhibitor can increase the NH4+-N strength by 33.4%.Under the combined application of biochar and nitrification inhibitor,the NH₄⁺-N strength is between the two separate treatments,and there is an interactive effect.Nitrification inhibitors could significantly reduce the strength of NO₂^--N by 23.4%.The NO₃^--N strength of adding biochar significantly increased by 15.8%,while the strength of adding nitrification inhibitor NO₃^--N decreased significantly by 29.8%.The combined application of the two was between the combined application of biochar and nitrification inhibitor.And it was significantly lower than that of N treatment.The results showed that the combined application of the two could inhibit the process of soil nitrification.Compared with nitrogen treatment,the addition of biochar increased the gene abundance of AOA and AOB,decreased the gene abundance of nis K and nir S,decreased the gene abundance of nir K and AOB by adding nitrification inhibitors,and decreased the gene abundance of nir S and AOB by the combined application of biochar and nitrification inhibitor.There was no significant effect on nos Z gene abundance in all treatments.(2)During the culture period,the N₂O emission rate of each treatment varied from 5.57 to 247.80ngkg-1h-1,and the cumulative N₂O emission of each treatment varied between 31.40-103.13?gkg^-1.Compared with the nitrogen fertilizer treatment,the combined application of biochar increased the N₂O emission rate by 37.4%at the emission peak,decreased the N₂O emission rate by 85.5%with nitrification inhibitor,and decreased the N₂O emission rate by 90.9%with the combined application of biochar and nitrification inhibitor.After the emission peak,the treatment of combined application of biochar decreased rapidly,while the combined application of nitrification inhibitor and both kept low emission;the addition of biochar reduced the cumulative N₂O emission by 15.1%,and the combined application of nitrification inhibitor decreased by 68.3%.The combination of the two was lower than that of individual application.The results showed that nitrification inhibitor had a stronger effect on N₂O emission from vegetable soil than biochar,and the effect of combined application of nitrification inhibitor and biochar was better.(3)During the culture period,the NO emission rate of each treatment varied from 19 to 4142ngkg¹h^-1,and the cumulative NO emission of each treatment varied from 506 to 1605?gkg^-1.Among them,all treatments reached the emission peak in 1 day and reached the secondary emission peak in 14 days.Taking 14 days as an example,decorative biochar reduced the NO emission rate by 4.58%,and the application of nitrification inhibitors reduced the NO emission rate by 68.03%,the combined application of the two reduced the NO emission rate by 92.06%.The combined application of biochar and nitrification inhibitors reduced the cumulative NO emissions by 41.55%,43.48%and 68.47%,respectively.Generally speaking,the combined application of biochar and nitrification inhibitors reduced the NO emissions by 68.47%.Generally speaking,the combined application of the two treatments has a better effect on NO emission reduction than single application.Overall,the addition of biochar and nitrification inhibitors combined with nitrogen fertilizer application had the effect of reducing emissions and reduced the emissions of N₂O and NO during the culture period.Biochar promoted the further reduction of N₂O during soil denitrification,while nitrification inhibitors could reduce the effect of biochar alone on stimulating nitrification,and the combined application of biochar and nitrification could achieve the goal of carbon sequestration and emission reduction.