| Soil amendment with biochar as is regarded as new ways to ensure the national food security,improve soil ecosystem function and solve environmental problems.Therefore,biochar has become hot issue in the field of soil and environment throughout the world.Biochar not only affects the intrinsic physical and chemical properties and biological characteristics,but also plays a key role in biogeochemical process,especially in the carbon and nitrogen cycle.In this study,the characterizes of biochar derived from maize straw prepared at 300?,450? and 600?were evaluated,and both pot and field experiments were conducted to investigate the effect of maize straw biochar(MC)on soil carbon(C),nitrogen(N)and microbial properties in a fluvo-aquic soil in the North China Plain,by the means of 15 N tracer,soil enzymology,molecular ecology techniques,etc,so as to illuminate the interaction mechanism of biochar,soil C and N.So,the main purpose of the study will provide the scientific foundation for the reasonable application of MC and N,increasing crop production and efficiency,and protecting farmland ecological environment.The main findings are as follows:(1)The elemental composition of MCs prepared at 300?,450? and 600?(i.e.,MC300,MC450,MC600)was mainly dominated by C,followed by oxygen(O)and then minor mineral elements(e.g.Ca,Mg,Si,P,K,etc.).As pyrolysis temperature increased,the pH,ash and C contents,surface area,pore volume,contents of aromatic C and basic groups in MC all increased while the yield,H and O contents,ratios of O:C and H:C,contents of alkylic C and surface acidic groups significantly decreased.Electrical conductivity(EC)and total contents of mineral elements such as water souble and exchangeable K,Na,Ca,Mg first increased and then decreased with the increase of pyrolysis temperature,with the MC450 showing the maximum values.Pyrolysis temperature had no significant affect on the variety of functional groups,but it significantly infuenced the richness of MC.Our experiment showed that the cross section of sample MC300 had an obvious tubular pore structure,with most of the pores adhering to some particular substances in their walls.The MC450 and MC600 samples had a smooth surface structure and holes with a small pore diameter could be observed on the surface of MC600.The outer surface profile of sample MC300 was slightly unclear and adhered to many particles,while the profiles of samples MC450 and MC600 showed a typical aligned and clear rectangular structure,with more and more thin cell walls.(2)The results of pot experiment found that pH value,organic C,total N,dissoved organic C,microbial biomass C and N in all MC-amended soils significantly increased compared with the MC0,while contents of the dissoved N and NO3-N decreased throughout the monitoring period.The contents of soil organic C,dissoved organic C,microbial biomass C and N(MBC,MBN)showed a reduced trend with increasing pyrolysis temperature.The results also showed that the MC450 treatment enhanced EC,total N at maturity period,and the MC300 treatment enhanced microbial biomass C and N contents.The fate of 15 N fertilizer was significantly influenced by pyrolysis temperature of MC.All MC-amended soil enhanced 15 N use efficiency while it reduced 15 N loss,with the MC450 treatment showing the highest 15 N use efficiency and the lowest 15 N loss.15 N use efficiency in the MC450 treatment was significantly higher than the MC0 by 7.2%,and 15 N loss rate was significantly lower than the MC0 by 8.2%.Soil enzyme activity has different responses to MCproduced at different pyrolysis temperatures.The MC could enhance the activities of soil organic N and carbohydrates decomposition enzyme.The MC600 reduced the activity of carbohydrates decomposition enzyme and increased the activity of organic N decomposition enzyme.The MC450-amended soil significantly increased the activities of ?-glycosidase,cellobiosidase and aminopeptidases.Soil total N and MBC were dominant factors affecting soil enzyme activities.The addition of MC increased the soil total PLFA,mole percentages of bacteria and actinomycetes,and decreased the ratio of G+/G-and fungus mole percentage.The changes in the microbial community composition were mainly related to soil NO3-N content.Generally,The MC450 was more effective strategy to enhance soil fertility,C storage and N use efficiency.(3)the results of field experiment showed that MC rates significantly affected the contents of soil nutrients,microbial biomass C and N and crop yield(P<0.01).The contents of soil organic C,total N,water soluble organic C,NO3-N and SOC/TN were significantly increased with the increase of MC,with the MC22.5 showing the largest increase and higher than the MC0 by 165.0%,74.1%,39.1%,75.1% and 44.0%,respectively.Soil MBC and MBN contents and crop yield obtained the maximum values at MC rate of 7.5 t/hm2(MC7.5),with the MC7.5 treatment showing largest increase and higher than the MC0 by 49.2%,57.6%,46.1%,respectively.The contents of SOC?DOC?NH4+-N?MBC?MBN and crop yield all first decreased and then increased with the increase of N rate,with the N150 treatment showing the maximum values and higher than the N0 by 29.7%,22.9%,44.8%,79.4%,115.3%,respectively.The crop yields in all N treatments were higher than the N0,but there were no significant differences among the three N treatments.Soil total N and MBC were dominant factors affecting soilC-and Ncycle enzyme activities.The changes in the microbial community composition were mainly related to soil pH and MBC contents.The MC7.5N150 treatment obtained the maximum crop yield,increased yields of wheat and maize by 17.18% and 22.65%,and saved N fertilizer by 33% compared with MC0N225 treatment,respectively.In conclusion,The MC450 was more effective strategy to enhance soil fertility,C storage and N use efficiency under MC prepared at 300?,450? and 600?.The N150MC7.5 treatment was more effective to improve soil fertility and maintain high crop yields in a short term,which could be used as an effective way of management practice. |
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