| Under the background of global warming,the carbonization of agricultural wastes has become a hot spot in the field of greenhouse gas emission reduction in farmland soil.Because of its unique properties,biochar has good carbon sequestration and emission reduction effects.However,it is not demonstrated that the effect of biochar and nitrification inhibitors on soil greenhouse gas emissions and enzyme activities in calcareous fluvo-aquic soil.Therefore,straw carbonization has been studied.The effect and mechanism of returning to the field and its combined application with nitrification inhibitors on soil greenhouse gas emissions can provide theoretical basis and reference for the utilization of straw resources,carbon sequestration and emission reduction,and sustainable agricultural development.The research was carried out in the Teaching and Research Base of Soil Ecological Environment of Liaocheng University,Dongchangfu District,Liaocheng City,Shandong Province.Using soybean straw as raw material,the research on the effects of straw returning and biochar combined with urea and nitrification inhibitors on soil greenhouse gas emissions and soil physical and chemical properties was studied.,The influence of soil enzyme activity,analysis of the correlation between various parameters,reveals the mechanism of biochar and nitrification inhibitors to achieve soil greenhouse gas emission reduction.The results are as follows:(1)Effect of soybean stover biochar on soil physicochemical propertiesCompared with the CK treatment,the addition of biochar increased the soil DOC and available potassium content by 8.58%and 45.24%,and reduced the nitrate nitrogen content by 67.72%.Compared with CK treatment,straw returning to the field increased the soil ammonium nitrogen,nitrate nitrogen,available phosphorus,and available potassium content by 4.57%,170.66%,3.33%,and 62.41%,respectively.Compared with pure urea treatment,the nitrification inhibitor combined with urea treatment increased the soil nitrate nitrogen content by 1.87%and reduced the soil available potassium content by18.82%.Compared with CK treatment,the content of DOC and available potassium in the soil of LBCN treatment increased by 9.64%and 14.29%,respectively,and the content of nitrate nitrogen decreased by 58.08%compared with CK treatment.(2)Effect of soybean stover biochar on soil enzyme activityCompared with CK treatment,the addition of biochar increased the soil alkaline phosphatase activity by 14.31%,and decreased the soil urease,nitrate reductase,and nitrite reductase activities by 14.21%,20.33%,and 22.81%,respectively.Compared with the CK treatment,straw returning increased the soil invertase,urease,alkaline phosphatase,and nitrite reductase activities by 87.65%,36.05%,54.48%,28.70%,and reduced the soil nitrate reductase activity by 51.71%.The combined application of nitrification inhibitor and urea reduced the soil alkaline phosphatase and nitrate reductase activities by 2.55%and 15.00%,respectively,compared with pure urea treatment.Compared with CK treatment,LBCN treatment reduced soil alkaline phosphatase and nitrate reductase by 4.08%and 6.35%,respectively.(3)Effects on soil greenhouse gas emissions soybean straw-based biocharThe CO2emissions of the treated soils showed an overall downward trend,and the N2O emissions of the soils increased first and then decreased.The emission peaks were mainly concentrated in the early stage.The CH4 emissions of the treated soils were mainly represented as CH4 sinks during the test period.The Global Warming Potential(GWP)decreases in the order of U>HSSU>HSSN>LSSU>LSSN>HSS>LSS>N>CK>HBCU>HBC>HBCN>LBC>LBCU>LBCN.After straw is applied to the soil,the GWP will increase,and the GWP will gradually increase with the increase of the amount of straw added.After biochar is applied to the soil,the GWP will be reduced,and the GWP will gradually decrease with the increase of the amount of biochar.Biochar combined with urea significantly reduced GWP,while the GWP of biochar+urea+nitrification inhibitor was lower than that of biochar+urea treatment.(4)Correlation analysis of soil greenhouse gas emissions,physicochemical properties,and enzyme activitiesSoil CO2 emissions have a very significant negative correlation with DOC and nitrate reductase,with correlation coefficients of-0.537 and-0.543,respectively,and a very significant positive correlation with ammonium nitrogen,nitrate nitrogen,available phosphorus,and alkaline phosphatase.The correlation coefficients are 0.639,0.487,0.596,0.433,respectively.Soil N2O emissions are significantly positively correlated with soil nitrate nitrogen and available phosphorus content,and the correlation coefficients are0.308 and 0.375,respectively.There is no significant correlationship between soil CH4emission and various physicochemical properties and enzyme activity indicators.(5)Optimization of combined application of biochar,nitrogen and nitrification inhibitorThe LBCN treatment had the smallest global warming potential during the experiment,indicating that the combination of biochar and nitrification inhibitor nitrogen fertilizer treatment can reduce soil greenhouse gas emissions.LBCN treatment effectively increases the content of DOC,available phosphorus and available potassium in the soil,and improves the activities of soil invertase and alkaline phosphatase.Considering the global warming potential,soil physicochemical properties and enzyme activity,it is recommended to mix 2.5 t·hm-2 biochar,40 kg·hm-2 urea and 0.37 kg·hm-2 nitrification inhibitor in the soil to realize farmland soil carbon sequestration,emission reduction and sustainable agriculture. |
PDF Full Text Request