| Reducing chemical nitrogen fertilizer application and increasing efficiency is one of the important measures to achieve zero growth of chemical fertilizer,which can boost the sustainable development of agriculture.In this study,field experiment and laboratory analysis were combined to replace fertilizer nitrogen application with is nitrogenous biochar,and 6 treatments were set: CK(no nitrogen fertilizer,only phosphate fertilizer and potassium fertilizer),conventional fertilization T0(chemical fertilizer nitrogen 100%),T1(chemical fertilizer nitrogen 90% + biochar nitrogen10%),T2(chemical fertilizer nitrogen 80% + biochar nitrogen 20%),T3(chemical fertilizer nitrogen 70% + biochar nitrogen 30%),T4(chemical fertilizer nitrogen 60%+ biochar nitrogen 40%).Before rice transplanting,biochar was evenly spread on the surface soil of paddy field,and then 50% of chemical nitrogen fertilizer,100% of phosphate fertilizer and 50% of potassium fertilizer were mixed and applied as base fertilizer.The remaining nitrogen fertilizer was divided into three topdressing and one topdressing of potassium fertilizer.In order to study the effects of biochar combined with nitrogen reduction on soil organic carbon active components,organic carbon mineralization and microbial community structure in yellow paddy soil,soil samples were sampled at maturity stage and cultured in laboratory.The main results are as follows:(1)Combined application of biochar and nitrogen reduction could significantly increase soil organic carbon(SOC)content(P<0.05,the same below),which was directly proportional to the proportion of biochar combined application with nitrogen reduction.Soil microbial biomass carbon(MBC),easily oxidized carbon(ROC),soil microbial biomass nitrogen(MBN)and MBN/TN all showed a trend of first increasing and then decreasing with the increase of biochar and nitrogen application ratio.Compared with CK treatment,T2 treatment significantly increased,while soil soluble carbon(DOC)content was the lowest in T2 treatment.Compared with T0 treatment,soil q MB(MBC/SOC),DOC/SOC and ROC/SOC decreased by 0-0.40,0.16-0.30 and 0.09-0.45 percentage points,respectively,T3 and T4 treatment significantly decreased.(2)The mineralization rate of organic carbon reached the peak value on the third day after the beginning of culture,decreased rapidly in the early stage(the third to the sixth day),slowly decreased in the middle stage(the sixth to the eighteenth day),and gradually stabilized in the late stage(the eighteenth to the thirtieth day).The dynamic change of mineralization rate with time accorded with the logarithmic function relationship(P<0.01).The cumulative organic carbon mineralization amount(Ct)and cumulative mineralization rate(Cr)were 0.55-0.86 g/kg and 2.9%-4.0%,respectively.Compared with T0 treatment,T2 treatment significantly decreased by 10.0% and 1.10 percentage points,respectively.(3)Proteobacteria(27.73%-35.93%)and Chloroflexi(17.91%-23.41%)were the main dominant bacteria in the treatment of soil bacteria by biochar combined with nitrogen reduction.Correlation analysis of environmental factors showed that bacterial Shannon index was significantly positively correlated with MBC and ROC,and significantly positively correlated with MBN.Simpson index was significantly negatively correlated with MBC and ROC,and significantly negatively correlated with MBN.ACE index and Chao index were positively correlated with ROC.The dominant fungi were Ascomycota(25.56%-52.33%)and Unclassified＿K＿＿fungi(13.01-32.21%).Correlation analysis of environmental factors showed that fungi Shannon index was positively correlated with 8 environmental factors.But not to significant level;Simpson index was negatively correlated with 8 environmental factors,only Ct reached significant level.ACE index was positively correlated with MBC.Chao index was positively correlated with MBC and MBN.In conclusion,combined application of appropriate amount of biochar and reduction of nitrogen fertilizer can effectively promote soil carbon fixation and fertilizer reduction. |
PDF Full Text Request