Maintaining good soil structural stability is an important element in agricultural sustainability. Incorporation of cereal straw and use of cover crops improve soil structural stability but the long-term individual and interactive effects of these management practices is poorly understood. We examined the impact of four rates of straw incorporation in spring barley (0, 4, 8 and 12 Mg ha⁻¹, annually) combined with a ryegrass cover crop undersown in the barley in spring. Soil was sampled after four decades of treatments in the Askov (Denmark) straw incorporation experiment situated on a sandy loam with 12% clay. We assessed clay dispersibility measured on two macro-aggregate size fractions (ClayDis 1–2 mm and ClayDis 8–16 mm), wet-stability of aggregates, and clay dispersibility of < 8 mm field-moist soil and aggregate strength. Soil structural stability and strength were related to soil organic carbon (SOC), SOC/Clay and root biomass. The SOC content increased with straw rate and when ryegrass cover crops were grown. Root biomass was marginally greater (P = 0.068), when cover crops were included. The soils receiving 8 and 12 Mg straw ha⁻¹ had a significantly lower ClayDis 1–2 mm and ClayDis 8–16 mm than soil with straw removal. Inclusion of a ryegrass cover crop did not affect ClayDis 1–2 mm, but decreased ClayDis 8–16 mm marginally (P = 0.054) and decreased clay dispersibility of field-moist soil. The results suggest, that binding agents from cover crops such as roots increase stabilization of large macro-aggregates, while the increased stability due to straw incorporation was related to SOC irrespective of aggregate size.

保持良好的土壤结构稳定性是农业可持续性的一个重要因素。谷物秸秆的掺入和覆盖作物的使用提高了土壤结构的稳定性，但对这些管理实践的长期个体和相互作用影响知之甚少。我们研究了四种秸秆掺入率对春大麦的影响（0、4、8 和 12 Mg ha ^-1，每年）与春季大麦中的黑麦草覆盖作物相结合。在位于含 12% 粘土的砂质壤土上的 Askov（丹麦）秸秆掺入试验中，经过 4 年的处理后对土壤进行取样。我们评估了在两种大骨料粒度级分（ClayDis 1-2 毫米和 ClayDis 8-16 毫米）上测量的粘土分散性、骨料的湿稳定性以及 < 8 毫米田间潮湿土壤的粘土分散性和骨料强度。土壤结构稳定性和强度与土壤有机碳 (SOC)、SOC/粘土和根生物量有关。SOC 含量随着秸秆用量和黑麦草覆盖作物的生长而增加。 当包括覆盖作物时，根生物量略大（P = 0.068）。接受 8 和 12 Mg 秸秆的土壤 ha ^-1与去除秸秆的土壤相比，ClayDis 1-2 mm 和 ClayDis 8-16 mm 显着降低。加入黑麦草覆盖作物不会影响 ClayDis 1-2 mm，但略微降低 ClayDis 8-16 mm ( P  = 0.054) 并降低田间潮湿土壤的粘土分散性。结果表明，来自覆盖作物（如根）的粘合剂增加了大团聚体的稳定性，而由于秸秆掺入而增加的稳定性与 SOC 相关，而与团聚体大小无关。