长期秸秆覆盖对免耕稻-麦产量、土壤氮组分及微生物群落的影响

Long-term Straw Mulching Affects Rice and Wheat Yields,Soil Nitrogen Fractions,and Microbial Community Under a No-till System

为探究长期秸秆覆盖对免耕区作物产量、土壤氮素组分及微生物群落特征的影响,以稻-麦定位免耕试验为研究对象,选取了其中免耕且秸秆移除和免耕且秸秆覆盖2个处理,于试验开展第12年(2018年)小麦收获后,统计分析近五年产量数据,并采集各处理0~5、5~10、10~20、20~30 cm的土壤样品,测定土壤全氮及活性氮组分,利用磷脂脂肪酸(PLFA)方法表征土壤微生物群落。结果表明:(1)秸秆覆盖显著提高了小麦产量(增幅为6.49%),对水稻产量影响不显著。(2)秸秆覆盖对土壤氮组分的影响略有差异:它显著提高了土壤0~5 cm全氮、硝态氮和铵态氮以及0~10 cm颗粒有机氮、0~5 cm和10~20 cm可溶性有机氮含量,对微生物生物量氮无显著影响;它提高了0~5 cm和10~20 cm可溶性有机氮占全氮的比例,对其他组分占全氮比例无显著影响。(3)秸秆覆盖显著提高了土壤微生物总PLFA和细菌PLFA丰度,对真菌PLFA和放线菌PLFA无影响,降低了土壤真菌/细菌比;微生物生物量氮、土壤全氮、颗粒有机碳/颗粒有机氮比是显著影响土壤微生物群落组成的关键土壤环境因子。(4)无论秸秆覆盖与否,土壤全氮、活性氮组分含量和微生物组分均表现出显著的深度效应。综上所述,秸秆还田提升了土壤氮素含量,提高了小麦产量,增加了土壤微生物总量,可在四川免耕稻-麦轮作区推广应用。

【Objective】Conservation tillage has attracted increasing attention over recent decades due to its benefits in improving soil quality.A 12-year fixed field experiment was conducted to assess the effects of long-term straw mulching on yields of rice and wheat,soil nitrogen fractions and microbial community with soil layers under a no-till system in Southwestern China.【Method】Two treatments,no-till without straw mulch(NT)and no-till with straw mulch(NTS),were used for the experiment.The soil was sampled at 0-5,5-10,10-20,and 20-30 cm soil layers.Soil total nitrogen(TN)and labile nitrogen fractions,including particulate organic nitrogen(PON),microbial biomass nitrogen(MBN),NH4+-N,NO3--N,and dissolved organic nitrogen(DON)were analyzed.Soil microbial community was determined using phospholipid fatty acid(PLFA)analyses.Crop yields were measured from September in 2013 to May in 2018.【Result】The results showed that compared to the NT treatment,the NTS treatment significantly increased wheat yield by 6.49%,with negligible effects on rice yield.The NTS treatment increased the contents of soil TN at 0-5 cm soil layer,NH4+-N and NO3--N at 0-5 cm layer,PON at 0-5 and 5-10 cm layers,and DON at 0-5 and 10-20 cm layers but not MBN content.Also,the NTS increased the DON/TN ratio at 0-5 and 10-20 cm layers rather than the ratios of other labile nitrogen fractions to TN.Soil total microbial PLFA and bacterial PLFA were higher in the NTS than in the NT treatment.Additionally,fungal and actinobacterial PLFA were comparable between the two treatments,leading to a lower fungal/bacterial ratio in the NTS.Principal component analysis revealed that the soil microbial community at 20-30 cm layer was separated from the other three soil layers,and soil microbial communities of NTS treatments were generally separated from NT treatments along the first principal component axis.Furthermore,redundancy analysis demonstrated that soil MBN,TN,and ratio of particulate organic carbon to PON were key factors in shaping soil microbial community.Soil TN,labile nitrogen fractions,and microbial PLFA fractions decreased with increased soil layers,irrespective of straw mulching status.【Conclusion】Straw mulching should be recommended to no-till systems in Sichuan province,Southwestern China because it leads to effective improvements in soil nitrogen contents,wheat yields,and soil total microbial PLFA.