秸秆覆盖对冬小麦农田土壤有机碳及其组分的影响

通过对黄土高原旱塬区冬小麦地4种覆盖方式下(无覆盖对照处理(CK)、全生育期9 000kg/hm~2秸秆覆盖(M1)、全生育期4 500kg/hm~2秸秆覆盖(M2)和夏闲期9 000kg/hm~2秸秆覆盖(SM))土壤的田间定位试验和室内分析,探讨不同秸秆覆方式对冬小麦地土壤有机碳及其组分含量以及各组分之间相关性的影响。结果表明:(1)较CK(无覆盖对照)处理,M1(全生育期9 000kg/hm~2)、M2(全生育期4 500kg/hm~2)和SM(夏闲期9 000kg/hm~2)处理,均显著增加0—10cm和10—20cm土层的土壤有机碳、微生物量碳、潜在矿化碳和颗粒有机碳含量(p0.05),而20—40cm土层差异不明显,其中M1(全生育期9 000kg/hm~2)处理效果最佳,SM(夏闲期9 000kg/hm~2)处理作用相对较弱。(2)不同覆盖方式影响土壤微生物量碳、潜在矿化碳和颗粒有机碳在总有机碳中的分配比例,土壤微生物量碳、潜在矿化碳和颗粒有机碳的相对含量变化范围分别为1.96%~3.31%,2.83%~3.78%,18.13%~37.25%。(3)各覆盖方式下土壤有机碳及其组分含量都随着土层的逐渐深入而下降,且土层越深,变化越趋于缓慢。(4)不同覆盖方式下的土壤有机碳及其组分含量两两之间均达到了极显著正相关关系(p0.01),颗粒有机碳、微生物量碳和潜在矿化碳与土壤有机碳的相关系数依次为:0.847,0.700,0.614,可见微生物量碳、潜在矿化碳、颗粒有机碳含量在一定程度上决定于土壤有机碳的贮存量。综上所述,秸秆覆盖对土壤有机碳及其组分含量具有增加效应,全生育期9 000kg/hm~2秸秆覆盖方式实际运用价值较高。颗粒有机碳和微生物量碳的动态变化更能反映土壤有机碳的早期变化,是土壤肥力变化更加敏感的指标。

Effects of Straw Mulching on Soil Organic Carbon and Fractions of Soil Carbon in a Winter Wheat Field

The effects of different mulching patterns on soil organic carbon,carbon components,and the relationships among carbon components on the Loess Plateau were investigated by carrying out a field positioning test and laboratory analysis.Four treatments were set up,including a control without mulching treatment (CK),straw mulching at a rate of 9 000 kg/hm2(M1),straw mulching at a rate of 4 500 kg/hm2 (M2) during winter wheat growing season,and straw mulching at a rate of 9 000 kg/hm2 (SM) during fallow summer.The main results were as follows:(1) Compared with CK,the M1,M2,and SM treatments could increase the contents of soil organic carbon,microbial biomass carbon,potential mineralized carbon,and particulate organic carbon significantly (p ＜ 0.05) at the depth of 0-10 cm and 10-20 cm,but not significantly at the depth of 20-40 cm.The effect of M1 treatment was the best among different mulching patterns,and the effect of SM treatment was relatively weak.(2) Different straw mulching influenced the proportion of soil microbial biomass carbon,potential mineralized carbon,and particulate organic carbon in total organic carbon.The relative content of soil microbial biomass carbon,potential mineralized carbon,and particulate organic carbon was 1.96％-3.31％,2.83％-3.78％,and 18.13％-37.25％,respectively.(3) The content of soil organic carbon and its components decreased with the deepening of soil layer,and the deeper the soil layer was,the more slowly the change was.(4) There was a significant positive correlation between soilorganic carbon and its components in different mulching treatments (p ＜ 0.01),the correlation coefficient of particulate organic carbon,microbial biomass carbon,and potential mineralized carbon with soil organic carbon was 0.847,0.700,and 0.614,respectively.It was suggested that microbial biomass carbon,potential mineralized carbon,and particulate organic carbon content depended on the storage of soil organic carbon.In conclusion,straw mulching could increase the contents of soil organic carbon and its components.A rate of 9 000 kg/hm2 had a higher practical application value.The dynamic changes of particulate organic carbon and microbial biomass carbon could reflect the early changes of soil organic carbon.Particulate organic carbon and microbial biomass carbon could indicate the changes of soil fertility more sensitively.