绿肥填闲种植对旱作冬小麦农田土壤团聚体有机碳含量的影响

依托黄土塬区4 a绿肥填闲种植田间定位试验，开展不同填闲作物对土壤团聚体组成及各组分有机碳在团聚体中分布影响的研究，为阐明填闲种植措施下土壤有机碳库的物理保护机制提供依据。试验设置4个处理，即冬小麦夏闲期种植长武怀豆(SB)、苏丹草(SG)、怀豆/苏丹草混播(Mix)和裸地休闲(CK)。利用干筛法将全土筛分为>5 mm、2～5 mm、0.25～2 mm和<0.25 mm等4个粒级，分别测定土壤和各粒级团聚体中有机碳和颗粒有机碳含量，进而计算团聚体平均重量直径及有机碳贡献率。结果表明：绿肥种植对土壤团聚体分布有显著影响，各绿肥处理均有利于0～10 cm土层土壤团聚体的形成，但对亚表层土壤团聚结构影响较小。与CK相比，在0～40 cm各土层，SB、SG和Mix处理均显著提高土壤有机碳含量、颗粒有机碳含量及团聚体平均重量直径，提高幅度分别为7.9%、8.0%和7.9%,其中SB更有利于表层土壤有机碳的固存，且土壤有机碳和颗粒有机碳含量之间呈显著正相关关系，这两者与团聚体平均重量直径之间均呈显著负相关关系。不同处理下土壤团聚体各有机碳组分含量存在差异，与CK相比，SB和Mix均显著...

Effect of green manure cover cropping on soil aggregate\|associated organic carbon in a dryland winter wheat field

Based on a 4-year field experiment in the Loess Plateau, the effects of green manure cover cropping on soil aggregates and aggregate\|associated organic carbon were studied. Three cover crops including Changwu soybean (SB), Sudan grass (SG), Changwu soybean/Sudan grass mixture (Mix) and a control with no cover crop (CK) were set during summer fallow period under winter wheat monoculture. Dry sieving method was used to sieve the whole soil into >5 mm, 2~5 mm, 0.25~2 mm and <0.25 mm size class for soil aggregation measurements. The contents of organic carbon and particulate organic carbon in the soil and each size class aggregate, aggregate mean weight diameter and contribution of soil organic carbon were determined separately. The results showed that cover cropping had a significant effect on soil aggregates distribution. Cover crop enhanced the formation of soil aggregates at 0~10 cm soil layer but had little impact on subsoils. Compared to CK, SB, SG and Mix significantly increased soil organic carbon content, particulate organic carbon content and aggregate mean weight diameter at 0~40 cm depths by 7.9%, 8.0% and 7.9%, respectively. SB group was more beneficial to soil carbon sequestration in the surface layer than SG and Mix. Soil organic carbon content and particulate organic carbon content showed a significant positive correlation, both of which had a significant negative correlation with aggregate mean weight diameter. The contents of aggregate\|associated organic carbon varied with cover crop treatments and soil depths. Compared with CK, SB and Mix significantly increased the contents of organic carbon and particulate organic carbon at 0~10 cm, and SG increased soil organic carbon content at 10~20 cm. Although <0.25 mm aggregates had a greater aggregate\|associated organic carbon content than other size classes, more than 80% of organic carbon fractions in aggregates was from >0.25 mm aggregate. In addition, cover cropping increased the contributions of >5 mm aggregate\|associated organic carbon and particulate organic carbon, indicating organic carbon were sequestrated in the >5 mm aggregates with cover crops. In conclusion, planting cover crops especially Changwu soybean effectively improved soil carbon storage and promoted the distribution and retention of aggregate organic carbon pool in the dry farming area of the Loess Plateau.