The impact of soil compaction on soybean root growth and grain yield can be alleviated by the presence of biopores and root channels in the soil profile. We hypothesize that cover crops (ruzigrass and oats) are better than grain crops (wheat and maize) to reduce the soil physical limitation to soybean root growth. We aimed to identify which precrops have higher potential to reduce the mechanical and water stresses resulting from soil compaction and soil desegregation, and to enhance soybean (Glycine max L) root growth and yield in an Oxisol (Rhodic Eutrudox), with clayey soil texture. Soybean was grown after four precrops (ruzigrass, oats, wheat, or maize), under four soil compaction levels [soil chiselling (MTC), no-tillage (NT), NT additionally compacted with four passes of a tractor (NTCT), and NT additionally compacted with eight passes of a grain harvester (NTCH)]. Soil physical attributes (bulk density, macroporosity, water-filled pore space and soil penentration resistance) in the soil profile (0−50 cm) and soybean components (grain yield, cumulative root length density and root dry mass) were investigated. Soil physical attributes were improved over time due to the combined effects of natural wetting-drying cycles and biopores created by the roots of precrops. Ruzigrass increased soybean root biomass and length density, mainly at deeper soil layers of compacted treatments (NTCT and NTCH). The rate of increase of soybean root length density in the soil profile was higher after ruzigrass cultivation in comparison with maize and oats. Soil compaction effects on grain yield were partially (NTCH) or totally (NTCT) alleviated after two years and ruzigrass intensified the mitigation process. Ruzigrass also resulted in higher soybean yields in comparison with maize, whereas NTCH and MTC reduced yields in approximately 400 kg ha⁻¹ (∼13 %) compared to NT and NTCT. Soil strengthening was more evident after ruzigrass and oats cultivation than maize or wheat cropping. Soil compaction in clayey Oxisols can be alleviated over time as a result of root channels provided by precrops combined with natural wetting-drying cycles. Among the evaluated precrops, ruzigrass is of particular interest, as it provides the most suitable soil physical environment for soybean root growth and grain yield. In contrast, chiselling was demonstrated to be a non-viable strategy to mitigate soil physical constraints for root growth and grain yields.

土壤剖面中存在生物孔和根部通道可以减轻土壤压实对大豆根系生长和谷物产量的影响。我们假设覆盖作物（紫杉和燕麦）比谷物作物（小麦和玉米）更好，以减少土壤对大豆根系生长的物理限制。我们旨在确定哪些前茬作物具有较高的潜力，可以减少土壤压实和土壤解离而产生的机械应力和水分胁迫，并增强大豆（大豆L）在具有粘性土壤质地的Oxisol（Rhodic Eutrudox）中，根系生长和产量。四个前作作物（紫菜，燕麦，小麦或玉米）在四个土壤压实水平下（土壤chi割（MTC），免耕（NT），另外用拖拉机四次通过（NTCT）压实的NT）和NT还通过谷物收获机（NTCH）的八次通过进行了压实]。研究了土壤剖面（0-50 cm）中的土壤物理属性（堆积密度，大孔隙度，充满水的孔隙空间和抗土壤渗透性）和大豆成分（谷物产量，累积根长密度和根干质量）。由于自然的干湿循环和前茬根部产生的生物孔隙的共同作用，土壤的物理属性随时间而改善。紫苏提高了大豆根的生物量和长度密度，主要在较深的土壤层进行压实处理（NTCT和NTCH）。与玉米和燕麦相比，紫杉栽培后土壤剖面中大豆根长密度的增加速率更高。两年后，土壤压实对谷物产量的影响部分缓解（NTCH）或全部缓解（NTCT），而紫苏草加剧了缓解过程。与玉米相比，Ruzigrass的大豆单产也更高，而NTCH和MTC的单产减少了约400 kg公顷 两年后，土壤压实对谷物产量的影响部分缓解（NTCH）或全部缓解（NTCT），而紫苏草加剧了缓解过程。与玉米相比，Ruzigrass的大豆单产也更高，而NTCH和MTC的单产减少了约400 kg公顷 两年后，土壤压实对谷物产量的影响部分缓解（NTCH）或全部缓解（NTCT），而紫苏草加剧了缓解过程。与玉米相比，Ruzigrass的大豆单产也更高，而NTCH和MTC的单产减少了约400 kg公顷与NT和NTCT相比，为^-1（〜13％）。种植紫杉和燕麦后，土壤强化比玉米或小麦种植更明显。由于预茬作物提供了根部通道，加上自然的干湿循环，随着时间的流逝，可以减轻粘土质土壤中的土壤压实。在评估的前茬中，紫杉尤其受关注，因为它为大豆根的生长和谷物产量提供了最合适的土壤物理环境。相比之下，凿凿已被证明是减轻土壤对根系生长和谷物产量的物理限制的可行策略。