Consistent Effect Of Biochar Amendment On Soil Quality,Rice Yield And Greenhouse Gas Emissions

Biochar is the highly arimatic substance remaining after pyrolysis of biomass such as crop-stalk or wood under complete or partial exclusion of oxygen. Biochar applied to cropland soil not only improves soil quality and enhance crop yield but also decreases greenhouse gas emissions. This experiment was conducted in a site-special experimental field involving N fertilizer treatments (0kg N·hm-2和240kg N·hm-2) and biochar level (0,20和40t·hm-2) in Sichan province in2011. It is investigated that residual effect of biochar on soil quality, crop yield and greenhouse gas emissions with and without N fertilization on the basis of existing experimental arrangment. And we evaluated synthetically consistent impact of biochar combining with the exsiting observation. The main results are as follow:(1)Effect of biochar on soil quality of the next year with or without N fertilizationRegardless of nitrogen fertilizer, biochar amendments increased soil organic carbon(SOC), total nitrogen(TN), pH value but decreased bulk density(BD) and NO3--N of soil in2011rice-growing season. Biochar significantly decreased microbial biomass C (MBC) and microbial biomass N (MBN) at the rate of40t·hm-2and significantly increased soil nitrifying activity at the rate of20t·hm-2, but did not significantly affect cold water extracted carbon(CWEC) and hot water extracted carbon(HWEC) When no N fertilizer was applied. Under N fetilizer treatments, biochar significantly increased CWEC and MBC, but significantly decreased soil nitrifying activity at the rate of40t·hm-2. Biochar significantly increased HWEC at the rate of20t·hm-2, but had no significant effect on MBN when N fertilizer was applied.(2)Effects of biochar on rice yield and yield components of the next year with or without N fertilizationBiochar significantly decreased tillers number, plant height and effective panicle number of rice, but did not significantly affect spikelets per panicle, seed setting,1000-grain weight and rice yield under no fertilizer-N applization. Biochar could decrease mortal tillers, but did not significantly affect plant height, effective panicle number, spikelets per panicle, seed setting,1000-grain weight and rice yield when N fertilizer was applied.(3)Effects of biochar on soil CH4, N2O and CO2emissions of the next year with or without N fertilizationBiochar did not significantly affect soil CH4and CO2emissions, but significantly decreased N2O emissions by73.7%and77.0%at the rate of20and40t·hm-2under no fertilizer-N application. Biochar significantly increased soil CH4by323.0%at the rate of40t·hm’2and soil CO2by24.1%at the rate20t·hm-2, but significantly decreased N2O emissions when N fertilizer was applied. For global warming potential (GWP) and greenhouse gas intensity(GHGI) from CH4and N2O emissions, biochar significantly decreased GWP and GHGI at the rate20and40t·hm-2under no fertilizer-N application, but biochar significantly decreased GWP and GHGI at the40t-hm’2when N fertilizer was applied.(4)Consistent effects of biochar on soil quality, rice yield and GHGs emissions with or without N fertilizer.Under no fertilizer-N application, biochar effect on enhancing SOC, TN, pH and decreasing BD could be stable in both cycle, but biochar effect on stablizing rice yield could become weaker at the rate of40t·hm-2in the subsequent cycles than in the first cycle. When N fertilizer was applied, biochar effect on enhancing SOC, TN and stabilizing rice yield could be stable in both cycles. Biochar effect on enhancing pH could become weaker at the rate of20thm-2, but decreasing BD could become strong at the rate of40t·hm-2in the subsequent cycles. Biochar effect on increasing soil CH4and CO2emissions could become weaker, but decreasing soil N2O emissions could become stronger in the subsequent cycles under no fertilizer-N application. Biochar effect on increasing soil CH4and CO2could become stronger but decreasing soil N2O could be stable in the subsequent cycles than in the first cycle when N fertilizer was applied. In both cycles, biochar effect on decreasing carbon intensity could be stable at the rate of40t·hm-2when N fertilizer was applied.