| The greenhouse gases(N2O,CH4,and CO2)emissions and NH3 volatilizations losses from soil in intensive greenhouse vegetable production are severe,which leading to a significant waste of fertilizer resources and exacerbation of air pollution issues.As a soil conditioner,biochar not only improves soil physical and chemical properties,but also plays an important role in carbon sequestration and emissions reduction.Nitrification inhibitors(NIs)can inhibit soil nitrification and then reduce soil greenhouse gases emissions,but there is a risk of increased NH3 volatilizations.It is speculated that the combined applications of biochar and nitrification inhibitor has a synergistic effect in reducing soil greenhouse gases emissions and NH3 volatilizations.Therefore,based on a literature review,this study used a combination of indoor aerobic cultivation and pot simulation methods to screen the suitable types of biochar which can achieve the combination reduction of soil greenhouse gases emissions and NH3 volatilizations,as well as the appropriate amount of biochar combined with nitrification inhibitors.In addition,the reduction effect of biochar combined with nitrification inhibitors on soil greenhouse gases emissions and NH3 volatilizations were also clarified and its microbial impact mechanism were also preliminarily revealed in this study,which provides a scientific theoretical and technical basis for the green and high-quality development of greenhouse vegetable production,as well as the applications of biochar and nitrification inhibitors.The main research findings are as follows:(1)Through literature review,the characteristics of biochar properties for achieving the combination reduction of soil greenhouse gases and NH3 emissions were identified.Based on the comprehensive analysis,biochars with the calcination temperature ranging from 400℃ to 600℃,specific surface area ranging from 3.29 to 790 m2/g,and relatively high content of acidic functional groups have a significant effect on reducing soil greenhouse gases emissions and NH3 volatilizations,providing a good reference for later biochar screening work.(2)The biochar species with the best effect on greenhouse gases emissions and NH3 volatilizations in greenhouse vegetable soil have been selected.Based on the comprehensive analysis of global warming potential(GWP),compared with conventional nitrogen applications,the wheat straw charcoal,corn straw charcoal,bamboo charcoal,and wood charcoal at temperatures ranging from 400℃ to 600℃can significantly reduce the total GWP,with a range of 4.46%to 9.58%.Under the equal nitrogen conditions,both rice straw charcoal and bamboo charcoal significantly reduced total GWP by 6.91%and 7.20%,respectively.Compared with conventional nitrogen applications,biochar can effectively reduce soil NH3 volatilizations,ranging from 12.97%to 28.40%.Results of comprehensive analysis showed that the bamboo charcoal prepared at 400℃～600℃ has the best synergistic effect in reducing greenhouse gases and NH3 emissions in the soil.(3)The appropriate amount of biochar(bamboo charcoal)for combined applications with nitrification inhibitors to achieve the combination reduction of soil greenhouse gases and NH3 volatilizations has been selected.The combination applications of bamboo charcoal at the ratio of 0.5%,1%,and 2%with DCD at the rate of 15%can significantly reduce soil N2O and CO2 cumulative emissions,with a reduction range of 25.81%to 49.51%and 6.39%to 21.37%,respectively.Based on comprehensive analysis of GWP,the combination of bamboo charcoal and DCD can significantly reduce the total GWP,ranging from 7.52%to 21.82%.The combined applications of 0.5%and 2%bamboo charcoal and DCD had little effect on soil NH3 volatilizations.However,the combined applications of 1%bamboo charcoal and DCD significantly reduced soil NH3 volatilizations compared to CN and ON,with reductions of 22.35%and 16.67%,respectively.Overall comparison,the combined applications of 1%bamboo charcoal and DCD has the best comprehensive effect in reducing soil greenhouse gases and NH3 volatilizations.(4)The combination applications effect of 1%bamboo charcoal biochar and nitrification inhibitor DCD was validated in reducing greenhouse gases emissions and NH3 volatilizations in greenhouse vegetable soil.Throughout the entire growth period,the single applications of bamboo charcoal or DCD can significantly reduce the cumulative soil N2O emissions,ranging from 9.09%to 27.27%.The applications of nitrogen fertilizer combined with bamboo charcoal can significantly increase the cumulative soil CO2 emissions,while the applications of DCD or the combination applications of DCD and bamboo charcoal has no significant effect on reducing CO2 emissions.The combined applications of bamboo charcoal and DCD has little effect on the total GWP,and did not show a synergistic effect in reducing greenhouse effects.The combination of nitrogen fertilizer and DCD significantly increased the accumulation of soil NH3 volatilizations compared to the single applications of nitrogen fertilizer.The bamboo charcoal or the combination applications of biochar and DCD can significantly reduce soil NH3 volatilizations,with a decrease of 31.03%and 38.42%,respectively.In addition,the combined applications of bamboo charcoal and DCD can significantly increase the Vc content of the fast vegetable,with little effect on chlorophyll content,nitrate content,and soluble sugar content.(5)Analyzed the correlation between tomato soil greenhouse gases emissions,soil NH3 ammonia volatilizations,and soil nitrogen related functional genes.There is a highly significant negative correlation between soil CO2 accumulation and nosZ,with a correlation coefficient of-0.68.There is a highly significant negative correlation between total GWP and nosZ,with a correlation coefficient of-0.66.The total GWP of soil is mainly determined by N2O and CO2,and there is a highly significant positive correlation with them,but there is no significant correlation with other functional microorganisms.Through comprehensive evaluation,it was found that the combination of bamboo charcoal 1%and nitrification inhibitor DCD has a significant effect on reducing soil greenhouse gases emissions and NH3 volatilizations in greenhouse vegetable production.This provides an important basis for reducing greenhouse gases emissions and NH3 volatilizations in greenhouse vegetable fields,reducing nitrogen gaseous losses,and improving nitrogen utilization efficiency. |
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