耕作方式和秸秆还田对华北地区农田土壤水稳性团聚体分布及稳定性的影响

本研究基于10年耕作措施的定位试验，利用湿筛法研究了不同耕作措施和秸秆还田条件下农田土壤水稳性团聚体的分布规律，并利用平均重量直径（MWD）和几何平均直径（GMD）评价了不同处理水稳性团聚体的稳定性。研究结果表明，不同耕作措施处理的水稳性团聚体在0~10cm，10~20cm和20~30cm土层表现出不同的分布趋势，随着土层的加深，各处理水稳定团聚体的分布呈粒径逐渐减小、分布范围逐渐扩大趋势，0~10cm土层的水稳性团聚体多集中于2~5mm粒径范围，10~20cm土层水稳性团聚体多集中在0.5~5mm粒径范围，以0.5~1mm最多，而20~30mm，则广泛分布在0.25~5mm粒径范围。通过MWD和GMD值可以看出，免耕、耙耕和旋耕措施更能有效地保护表层（0~10cm）土壤水稳定团聚体的稳定性，常规耕作和深松处理则显著降低了20~30cm水稳性团聚体稳定性。秸秆还田显著增加了土壤有机碳（SOC）含量，且显著影响了土壤表层水稳性团聚体的稳定性。作用力分析结果表明，在0~10cm表层，秸秆作用在土壤表层显著影响了水稳定大团聚体的数量及其稳定性（P<0.001），多元回归分析说明其与土壤有机碳含量达到了极显著水平（P<0.01），且同时也受到来自耕作和秸秆交互效应的影响（P<0.01）；但在10~20cm土层，影响其数量分布的主要因素是不同的耕作措施及耕作和秸秆的交互效应（P<0.001）；而在20~30cm，耕作措施、秸秆和两者的交互效应共同对水稳性大团聚体数量产生重要的影响，但主要作用力来自耕作措施（P<0.001）和两者的交互效应（P<0.001）。免耕秸秆还田措施能显著提高土壤的水稳性团聚体的比例和稳定性。

Effects of different tillage and straw systems on soil water-stable aggregate distribution and stability in the North China Plain

Tillage and crop residue input are two important factors to effect on the distribution and stability of soil water-stable aggregation. The objective of this study was to evaluate the changes of soil water-stable aggregate distribution and stability after 10 years in response to long-term tillage and crop straw management experiment in winter wheat (Triticum aestivum Linn.) and maize (Zea mays L.) cropping system in the North China Plain. The experiment was laid out in a split-plot design, the main plots involved five tillage systems, which included no-till (NT), subsoiling (ST), harrow tillage (HT) and rotary tillage (RT), with the conventional tillage (CT) as the control; the subplots involved two residue management methods: straw returning (P) or straw removal (A). As a result, the distributions of soil water-stable aggregate revealed varied characters in the 0~10 cm, 10~20 cm and 20~30 cm layers under the different tillage and straw management treatments. The size class of soil water-stable aggregate decreased with the soil layers deepening, while the distribution range were increased, the main ranges in the 0~10-cm, 10~20-cm and 20~30 cm layers were 2~5 mm, 0.5~5 mm and 0.25~5 mm size classes, respectively. Suitable tillage combination with crop straw input increased the proportion and stability of water-stable macro-aggregate. The proportion and stability of water-stable macro-aggregate in the 0~10cm under the PS, PR, PH and PN treatments were significant higher than that of the straw removal treatments (P<0.05), and they significant related with the straw input (P<0.001) and the interaction between it and tillage (P<0.01). Meanwhile, the stability of water-stable macro-aggregate also correlated with the soil organic carbon (SOC) content of these straw returning treatments according to the multiple regression analysis (P<0.01). Crop straw input significant increased the content of SOC and more SOC accumulated at the top of soil under conservational tillage methods such as under PS, PR, PH and PN, their contents significant higher than that of AS, AR AH and AN, respectively, this result further impacted on the stability of aggregate in different treatments in the 0~10-cm layer, but the SOC level did not influence on the stability in the 10~20-cm and 20~30-cm layers. The highest proportions in the 10~20-cm and 20~30-cm layers were observed at the PS treatment, the main driving factor of this result in the 10~20-cm layer were the tillage (P<0.001) and the interaction between tillage and straw (P<0.001), while in the 20~30-cm layer were the straw (P<0.001) and the interaction between tillage and straw (P<0.001). No tillage combination with crop straw input could improve the proportion and stability of water-stability aggregate.