秸秆还田与长期连作棉田土壤水稳性团聚体特征

以棉花长期连作定点试验田为研究对象,研究秸秆还田对长期棉花连作土壤水稳性团聚体及有机碳分布的影响。试验设长期连作5、10、20 a和30 a的秸秆还田小区及长期棉花连作5、10 a和20 a无秸秆还田小区,共计7个处理,每个处理3个重复。结果显示:无秸秆还田条件下,随着连作年限的增加,土壤1~0.25 mm水稳性团聚体含量和团聚体中有机碳含量逐渐降低,0.053 mm水稳性团聚体含量逐渐增加;而秸秆还田可以显著提高长期连作棉田土壤中1~0.25 mm水稳性团聚体含量、团聚体平均重量直径(MWD)、几何平均直径(GMD)值及团聚体中有机碳含量;秸秆还田条件下随着连作年限的增加,土壤1~0.25 mm水稳性团聚体含量逐渐增加,0.053mm水稳性团聚体含量逐渐降低,且对0~30 cm耕作层土壤影响较大;与无秸秆还田相比,秸秆还田长期连作棉田,随着连作年限的增加,团聚体分形维数(D)逐渐降低,而无秸秆还田分形维数(D)逐渐增加,团聚体分形维数表现为随土层加深而增大,最后在20~30 cm处趋于稳定。说明秸秆还田显著提高长期连作棉田水稳性团聚体的稳定性,对改善土壤结构、提升土壤的肥力具有积极作用,能够缓解长期连作对土壤物理性状产生的不利影响。

Stalk returning and continuous cotton cropping on soil water stable aggregate

The objective of the experiment is to study the effect of straw incorporation on water stable aggregate dis-tribution and organic carbon in the continuous cropping cotton field,providing scientific basis for long-term continuous cropping of cotton .This experiment had seven treatments’of continuous cropping plots,four treatments of cotton straw returning .There were three replicates for each treatment,The four treatments with cotton straw included four continuous cropping plots,such as 5,10,20 and 30 years,the other three treatments were 5,10 and 20 years continuous cropping plots .The results showed that under without straw returning,with the year of continuous cropping increasing,the per-centage of 1~0 .25 mm water stable aggregate and water stable aggregate organic carbon were remarkably decreased,the content of <0 .053 mm water-stable aggregates was gradually increased .But straw returning could significantly improved the percentage of 1~0 .25 mm water stable aggregate,as well as MWD,GMD and water stable aggregate organic carbon of long-term continuous cropping .Besides,with the year of continuous cropping increasing,the percentage of >0 .25 mm water stable aggregate was remarkably increased,the content of <0 .053 mm water-stable aggregates was gradually decreased .The largest impact was detected for the 0~30 cm soil layer .Compared with no straw returning,straw return-ing and long-term continuous cropping cotton fields,with the time of continuous cropping increasing,fractal dimension (D)was gradually reduced,and aggregates fractal dimension performance increases with depth,and finally stabilized at 20~30 cm soil layer .Straw returning significantly improved the stability of water stable aggregates under long-term continuous cropping .Straw returning has a positive effect of improve soil structure and enhance soil fertility,thus mitigat-ing the negative effect of long-term continuous cropping on soil physical properties .