保护性耕作对土壤团聚体及其有机碳含量的影响

Effect of Conservation Tillage on Stability and Content of Organic Carbon in Soil Aggregates

为了探讨保护性耕作对旱作农田套作模式土壤团聚体的影响,在重庆北碚西南大学试验农场对传统耕作(T)、垄作(R)、传统耕作+覆盖(TS)和垄作+覆盖(RS)4种处理下的西南紫色土丘陵区小麦-玉米-大豆套作体系玉米大豆共生时期土壤团聚体进行筛分和测定分析。结果表明:在玉米条带,随着团聚体粒级的减小各处理间水稳性团聚体质量分数差异降低,且差异主要出现在>0.25mm粒级的大团聚体中。但是在小麦-大豆条带,不同处理的水稳性团聚体含量没有明显差异。不同土层的土壤水稳性团聚体含量趋势一致,大小排序为A1(>2mm粒级的团聚体)>A2(2～0.25mm粒级的团聚体)>M2(<0.053mm粒级的团聚体)>M1(0.25～0.053mm粒级的团聚体)。0-5cm土层>2mm粒级的团聚体含量在36.31%～54.84%之间,低于5-10cm土层的含量(55.22%～70.73%),耕作处理对土壤水稳性团聚体的影响主要表现在0-5cm土层中,5-10cm土层各处理间没有差异。不同粒级团聚体内有机碳含量大小排序为A2>A1>M1>M2,有机碳主要富集在2～0.25mm粒级的团聚体内,其中的水稳性团聚体有机碳含量变化尤其敏感。保护性耕作措施能显著提高土壤有机碳含量,虽然2～0.25mm粒级中的有机碳含量最高,但是它的质量分数较低,土壤总有机碳增加主要是由于>2mm粒级的土壤水稳性团聚体有机碳含量提高。在西南紫色土丘陵区小麦-玉米-大豆套作模式下,保护性耕作有利于改善土壤团聚体结构,增加大团聚体含量,促进土壤有机碳的固定。

Explore the effect of conservation tillage on soil aggregates in dry cropping farmland intercropping mode,the experiment was conducted in the experimental field in Southwest University in Beibei,Chongqing.The soil aggregates were sieved,measured and analyzed during the corn and soybean symbiotic.There were four treatments including T(traditional tillage),R(ridge tillage),TS(traditional tillage+straw mulching) and RS(ridge tillage+straw mulching),which were replicated three times.On the corn belt,difference of water-stable aggregates content among treatments decreased with the reduction of aggregates.It was mainly in the large>0.25mm aggregates.Whereas there were no significant differences in water-stable aggregate content among different treatments in the wheat-soybean belt.Different soil layers had consistent with the trend of soil water-stable aggregates content which ranked as A1(>2mm)>A2(2～0.25mm)>M2(< 0.053mm)>M1(0.25～0.053mm).The content of soil aggregates>2mm was 36.31%～54.84%in 05cm soil layer,it was lower than that(55.22%～70.73%)in 5-10cm soil layer.Tillage effects on soil water-stable aggregates mainly appeared in 0-5cm soil layer,there was no difference in 5-10cm soil layer.Organic carbon content of different size aggregates was ranked as A2>A1>M1>M2.Organic carbon was mainly concentrated in the agglomeration of 2～0.25 mm.It was sensitive to change in soil water-stable aggregate organic carbon content.Conservation tillage could significantly increase the content of soil organic carbon,although the 2～0.25mm fractions of organic carbon content was the highest,but its mass fraction was lowest,the main contribution of soil total organic carbon increased soil water-stable aggregate in >2 mm.The wheat-corn-soybean intercropping mode under conservation tillage could improve soil aggregate structure,increase the aggregate content,and promote the fixation of soil organic carbon of purple soil in the southwest hilly area.