不同秸秆还田方式对土壤团聚体稳定性及有机碳含量的影响

Effects of Different Straw Returning Methods on Soil Aggregate Stability and Organic Carbon Content

为解决东北西部半干旱区因不合理耕作导致土壤结构性状变差及有机碳含量下降的问题,通过田间定位试验,研究了不同秸秆还田方式下土壤团聚体组成、团聚体稳定性及有机碳在团聚体中的分布,以探究不同秸秆还田方式对东北西部半干旱区土壤团聚体稳定性及有机碳含量的影响,为合理利用秸秆和改良土壤提供理论依据与技术指导。采用定位试验与室内分析相结合方法,设置6个处理,包括轮耕(T1)、秸秆全覆盖(T2)、秸秆半覆盖(T3)、留高茬(T4)、秸秆碎混还田(T5)、未秸秆还田(ck)。秋收后采集0~20 cm耕层原状土,进行团聚体组成、有机碳含量分析。结果表明:与对照处理相比,T1、T3、T4、T5处理土壤,均以>2000μm粒级团聚体含量最高,占全部团聚体的45%~50%(P<0.05),<250μm粒级团聚体含量最小,仅占5%~11%(P<0.05)。与秸秆不还田(ck)相比,秸秆还田土壤团聚体的平均重量直径(MWD)与几何平均直径(GMD)有显著提高,其中T1处理增加最高;团聚体破坏率(PAD)、不稳定团粒指数(ELT)值的变化为ck>T2>T4>T5>T3>T1;秸秆还田显著增加了土壤有机碳的含量,增加幅度为18.37%~65.51%(P<0.05);除T4处理外,其他处理>2000μm和2000~500μm粒级有机碳含量均显著增加;>2000μm团聚体有机碳对土壤有机碳的贡献率也得到提升,其中T1处理最高,为30%。相关性分析表明,土壤有机碳含量与GMD、MWD值呈显著正相关。适宜的秸秆还田可以有效改善土壤结构,提高土壤团聚体的稳定性,并增加土壤有机碳含量,提高大团聚体有机碳对土壤有机碳的贡献率。不同还田方式中,轮耕还田方式效果最好,适合在东北西部半干旱区应用。

In order to solve the problems of soil structural deterioration and organic carbon content decline caused by unreasonable tillage in semi-arid area of western Northeast China,the composition and stability of soil aggregates,and the distribution of organic carbon in the aggregates under different straw returning methods were studied through field positioning test to explore the effects of different straw returning methods on soil aggregate stability and organic carbon content in the semi-arid area of western Northeast China,which will provide theoretical basis and technical guidance for rational utilization of straw and soil improvement.A combination of long-term positioning test and indoor analysis was used,6 treatments were set up,including rotation tillage(T1),straw full coverage(T2),straw semi-coverage(T3),high stubble(T4),straw crushed and mixed returning(T5)and no straw returning(ck).After autumn harvest,the undisturbed soil of the 0-20 cm plough layer was collected,and the aggregate composition and organic carbon content were analyzed.The results showed that compared with the control treatment,among the four soil treatments of T1,T3,T4,and T5,the aggregates with a particle size of>2000μm had the highest content,accounting for 45%-50%of the total aggregates(P<0.05),the content of aggregates<250μm was the smallest,accounting for only 5%-11%(P<0.05).Compared with no straw returning,the mean weight diameter(MWD)and geometric mean diameter(GMD)of soil aggregates with straw returning were significantly increased,and the increase in T1 treatment was the highest,and the changes of PAD and ELT values were ck>T2>T4>T5>T3>T1.Straw returning significantly increased the content of soil organic carbon,ranging from 18.37%-65.51%(P<0.05).Except for T4 treatment,other treatments could significantly increase the organic carbon content of>2000μm and 2000-500μm fractions.The contribution rate of organic carbon in aggregates>2000μm to soil organic carbon was also increased,among which T1 treatment had the highest contribution rate with a value of 30%.Correlation analysis showed that soil organic carbon content was significantly positively correlated with GMD and MWD values.Suitable straw returning to the field could effectively improve the soil structure,improve the stability of soil aggregates,increase the content of soil organic carbon,and improve the contribution rate of organic carbon from macroaggregates to soil organic carbon.Among the different returning methods,the rotation tillage method has the best effect,and is suitable for application in the semiarid area of western Northeast China.