玉米秸秆不同构件混合分解的非加和效应及其对土壤有机碳矿化的影响

目的]研究玉米秸秆不同构件混合分解的非加和效应及其对黄绵土土壤有机碳矿化的影响,为秸秆还田背景下坡地土壤CO2排放提供理论支撑。方法]采用室内模拟试验,试验设置无玉米秸秆土壤对照(CK)及4种玉米秸秆添加处理:茎+土壤(CKS)、叶+土壤(CKL)、鞘+土壤(CKLS)、混合玉米秸秆+土壤(CKM)。结果]培养结束土壤有机碳矿化累积排放量实测值显著高于预测值,且促进作用主要是由培养初期快速分解阶段(1~28d)导致的。培养结束后混合玉米秸秆剩余质量预测值明显高于实测值,且元素含量发生明显改变,其中全氮含量预测值明显低于实测值,C/N预测值明显高于实测值。培养结束后CKS处理土壤微生物碳含量明显高于其他几种处理,其他几种处理差异不显著;添加玉米秸秆处理土壤微生物量氮明显降低,相应的土壤微生物量C/N增大,CKS,CKL和CKM处理与CK处理差异达到显著水平。土壤可溶性有机碳(DOC)含量CKLS和CKM处理明显高于其他3种处理,CKS与CKL处理与对照差异不显著。结论]玉米秸秆不同构件按比例混合对玉米秸秆分解产生协同促进作用,混合分解过程促进氮累积。

Non-additive Effects of Different Components of Maize Straw on Soil Carbon Mineralization

Objective] To investigate the non-additive effect of different maize straw components on soil organic carbon (SOC) mineralization in loessial soil in order to provide technical support for soil CO₂ emissions.Methods] By laboratory incubation experiment, five treatments were set including soil with no maize straw addition (CK); soil with stalk litter addition (CKS); soil with leaf litter addition (CKL); soil with leaf sheath addition (CKLS) soil with mixed maize straw addition (CKM).Results] The amounts of observed soil accumulative carbon mineralization were significant higher than the predicted value in the end of experiment, and the promotion was mainly happened in the fast decomposition stage (1~28 d). The predicted remaining mass and carbon-nitrogen ratio were higher than the observed values, while the predicted content of soil total nitrogen was lower than the observed value in the end of experiment. The content of microbial biomass carbon (MBC) was the highest under CKS treatment, and there was no significant difference among other treatments. The content of microbial biomass nitrogen (MBN) showed a decreasing tendency, the MBC/MBN increased under litter addition treatments and the differences among CKS, CKL and CKM treatments and CK treatment was significant. The content of dissolved organic carbon (DOC) was higher under CKLS and CKM treatments than under other three treatments, and the difference between CKS and CKL treatments was not significant.Conclusion] To mix litter in proportion had a synergistic effect on litter decomposition, and the decomposition of mixed litter promoted litter nitrogen accumulation.