西北绿洲区间作模式对土壤团聚体组成及其有机碳含量的影响

间作种植有利于增加作物产量和提高资源利用效率，但目前关于间作对土壤有机碳的影响仍存在争议，为明确不同间作模式下土壤团聚体组成及其有机碳变化规律，本研究基于2016年在甘肃省武威市设置的间作模式定位试验，探究西北绿洲灌区间作种植模式对土壤团聚体的影响，试验包括7个处理：玉米单作（M）、豌豆单作（P）、油菜单作（R）、小麦单作（W）、玉米间作豌豆（M/P）、玉米间作油菜（M/R）和玉米间作小麦（M/W）。2019年10月作物收获后采集0~20 cm和20~40 cm土壤样品，分析不同间作模式下土壤团聚体及其有机碳含量。结果表明，间作处理有增加土壤水稳性大团聚体（>0.25 mm）和微团聚体（0.053~0.25 mm）含量以及降低黏粉粒（<0.053 mm）含量的趋势。与M处理相比，M/W和M/R处理显著增加了0~20 cm和20~40 cm土壤团聚体平均质量直径和平均几何直径，而M/P处理则与M处理无显著差异。间作模式增加了土壤及土壤团聚体有机碳含量，M/W处理0~20 cm土壤有机碳含量比M处理显著提高11.5%，M/R和M/W处理20~40 cm土壤有机碳含量则分别比M处理显著提高4.3%和9.6%。M/W处理增加了土壤有机碳储量，在0~40 cm土层，M/W处理土壤有机碳总储量比M处理显著提高10.2%，M/W处理有机碳储量的增加是由于0~40 cm土层>0.25 mm和0.053~0.25 mm土壤团聚体有机碳储量提升。研究表明，西北绿洲灌区间作种植模式增加了土壤团聚体稳定性和有机碳含量，有利于农田土壤固碳。

Effects of intercropping regimes on soil aggregate composition and their organic carbon content in an oasis area of northwest China

Intercropping is beneficial in increasing crop yield and improving resource utilization efficiency. However, there is still controversy on the effect of intercropping regimes on soil organic carbon(SOC). Therefore, clarifying the rules of soil aggregates and their SOC variations under different intercropping regimes can provide a theoretical basis for exploring the carbon sequestration mechanism of intercropping. This study was based on the field experiment of different intercropping regimes located in Wuwei, Gansu Province since 2016. There were seven treatments, including sole maize(M), sole pea(P), sole rape(R), sole wheat(W), maize/pea intercropping(M/P), maize/rape intercropping(M/R), and maize/wheat intercropping(M/W). Soil samples of 0~20 cm and 20~40 cm layers were collected after harvesting in October 2019. Then, soil aggregates and their SOC content under different intercropping regimes were analyzed. Intercropping indicated an increasing trend in the content of soil water stability macroaggregates(>0.25 mm) and micro-aggregates(0.053~0.25 mm) but a decreasing trend in the content of silt and clay(<0.053mm). Compared with the M treatment, the M/W and M/R treatments significantly increased the mean weight diameter(MWD) and geometric mean diameter(GMD) of soil aggregates in 0~20 cm and 20~40 cm soil layers. There was no significant difference in the MWD and GMD between M/P and M treatments. Intercropping regimes increased the organic carbon contents of soil and soil aggregates. The SOC content of the M/W treatment was 11.5% higher than that of the M treatment in the 0~20 cm soil depth. The M/R and M/W treatments increased the SOC content by 4.3% and 9.6% in the 20~40 cm soil depth compared with the M treatment, respectively. The M/W treatment significantly increased the SOC storage. In the 0~40 cm soil depth, the SOC storage of the M/W treatment was significantly higher than that of the M treatment by 10.2%. The increase of the SOC storage in the M/W treatment depended on the improvement of the SOC storage in the soil aggregates of >0.25 mm and 0.053~0.25 mm in the 0~40 cm soil layer. The intercropping systems increased the stability of soil aggregates and SOC content in the northwest oasis irrigation area, which was conducive to promoting soil carbon sequestration in the farmland.