Soil compaction caused by the use of heavy agriculture machinery in non-optimal soil conditions hampers crucial soil functions. Tyre inflation pressure and wheel load are well-known key drivers of compaction. The effects of traction and repeated wheeling are, however, not yet fully understood but may be of critical importance. We aimed to quantify the effects of traction and repeated wheeling on some soil structural properties independently in a compaction experiment conducted on a sandy loam at a soil water content near field capacity, using a tractor-trailer combination at two loads. The trailer was used in ‘standard’ and ‘offset’ steering modes, the latter referring to the mode in which measurements could be taken for the pass of a single towed and thereby passive trailer wheel (with one, two, three and six wheel passes). Penetration resistance was measured to 0.71 m depth and 100-cm³ soil cores were collected around 0.16 m depth for structural property measurements. In the offset steering mode, the measurements were made in the tractor tracks to investigate the effect of traction and in the trailer’s wheel track to investigate the effect of repeated wheeling (at 6.0 Mg static wheel load). The measurements were also collected for the standard steering configuration with the high towed load and from reference plots. Measurements on the soil cores comprised bulk density, porosity, and air permeability. We found a clear effect of traction on deformation of some soil structural properties, with no significant effects of the low drawbar pull but with substantial effects of the high drawbar pull. Reductions in air permeability and specific permeability were significant (89 % and 83 %, respectively) and indicated a densification and homogenisation of the soil. The effect of repeated wheeling was gradual and reasonably well explained by a linear fit to the number of wheel passes. After six passes with the passive wheel caused some soil structural properties to differ significantly from the reference soil, and resulted in approximately similar levels of bulk density, porosity, air permeability and specific permeability as the tractor with high drawbar pull. Still, the deformation was stronger for the single pass of the tractor with the high drawbar pull than for six repeated wheeling of the passive trailer wheel. These results highlight the substantial effect of traction on soil compaction. Yet, the mechanisms causing this deformation remain speculative until the propagation of horizontal stress through the soil profile is better understood.

在非最佳土壤条件下使用重型农业机械造成的土壤压实阻碍了关键的土壤功能。众所周知，轮胎充气压力和车轮载荷是压实的关键驱动因素。然而，牵引力和重复转动的影响尚未完全了解，但可能至关重要。我们的目的是在土壤含水量接近田间容量的砂壤土上进行压实实验，在两个负载下使用拖拉机-拖车组合，独立地量化牵引和重复轮转对某些土壤结构特性的影响。拖车用于“标准”和“偏移”转向模式，后者指的是可以对单个拖曳的被动拖车车轮（具有一、二、三和六轮通过）的通过进行测量的模式）。³在 0.16 m 深度附近收集土芯用于结构特性测量。在偏置转向模式下，在牵引车履带中进行测量以研究牵引力的影响，并在拖车的车轮履带中进行测量以研究重复转动的影响（在 6.0 毫克静态车轮载荷下）。还收集了具有高牵引载荷的标准转向配置和参考图的测量值。对土壤核心的测量包括容重、孔隙率和透气性。我们发现牵引力对某些土壤结构特性的变形有明显的影响，低牵引力没有显着影响，但高牵引力有显着影响。空气渗透率和比渗透率显着降低（89 % 和 83 %，分别）并表明土壤的致密化和均质化。重复轮转的影响是渐进的，并且可以通过与轮次通过次数的线性拟合得到合理的解释。被动轮六次通过后，导致一些土壤结构特性与参考土壤显着不同，并导致体积密度、孔隙率、透气性和比渗透率与具有高牵引力的拖拉机大致相似。尽管如此，与被动拖车车轮的六次重复转动相比，具有高牵引力的牵引车单次通过的变形更大。这些结果突出了牵引对土壤压实的实质性影响。然而，