Large-scale sugarcane plantation is characterized by successive and disordered traffic of heavy machinery and equipment over the cycle, which can cause damage to the soil structure. As the stress induced by traffic exceeds the soil load-bearing capacity, it results in soil compaction. However, the mechanisms and key variables that govern the compressive characteristics in agricultural unsaturated soils to support those applied loads without plastic deformations (compaction) is not fully understood. To investigate this process, we measured the strength, swelling and compressibility characteristics of unsaturated soils with contrasting texture from sugarcane fields. Undisturbed soil cores were sampled in nine cultivated sugarcane fields, equilibrated at a matric potential of –100 hPa and subjected to confined uniaxial compression tests. Precompression stress (σ_p), compression (λ) and swelling (κ) indexes were extracted from the soil compression curves. Soil organic C (SOC), degree of compactness, total porosity and particle size fractions were also measured and correlated to the compressive parameters σ_p, λ and κ. Principal components, correlation and multiple regression models were used to the data analyses. Overall, reductions in soil strength and increases in the soil compressibility and elasticity occurred with the increase in SOC, whereas increases in the degree of compactness resulted in higher soil strength and lower soil compressibility and elasticity. Furthermore, our results revealed that silt + clay content considerably increased soil compressibility. In combined scenarios for a range of soil texture, SOC and degree of compactness at matric potential at around field capacity (i.e. –100 hPa), the maximum σ_p observed was approximately 200 kPa, which is a much lower load-bearing capacity than the estimated stress for some trucks and trailers used in sugarcane harvest (∼600−800 kPa). Our study suggests that soil compaction is eminent in sugarcane fields at matric potential close to field capacity, and can be aggravated in clayey soils with high SOC content and low degree of compactness. Therefore, urgent strategies of traffic control are necessary to prevent or mitigate soil compaction induced by mechanized sugarcane operations.

大规模的甘蔗种植园的特点是，整个周期内重型机械设备的运输连续而无序，这可能会破坏土壤结构。由于交通引起的应力超过土壤的承重能力，因此导致土壤压实。但是，尚不完全了解控制农业不饱和土壤的压缩特性以支持那些施加的载荷而没有塑性变形（压缩）的机理和关键变量。为了研究这一过程，我们测量了来自甘蔗田的具有对比质地的非饱和土壤的强度，溶胀和可压缩性特征。在9个耕种的甘蔗田中取样未扰动的土壤核心，在–100 hPa的基质势下进行平衡，并进行了受限的单轴压缩试验。_p），从土壤压缩曲线中提取压缩指数（λ）和溶胀指数（κ）。还测量了土壤有机碳（SOC），压实度，总孔隙度和粒径分数，并将其与压缩参数_σp关联，λ和κ。主成分，相关性和多元回归模型用于数据分析。总体而言，随着SOC的增加，土壤强度降低，土壤可压缩性和弹性增加，而致密度的增加导致土壤强度更高，土壤可压缩性和弹性降低。此外，我们的结果表明，粉土和粘土含量大大提高了土壤可压缩性。在一定范围的土壤质地，SOC和基质电势下的紧实度的组合方案中，在大约田间持水量（即–100 hPa）下，最大_σp观察到的压力约为200 kPa，这比甘蔗收获中使用的某些卡车和拖车的估计应力要低得多（〜600-800 kPa）。我们的研究表明，在甘蔗田中，基质势接近田间持水量时，土壤压实作用突出，而在高SOC含量和低压实度的黏性土壤中，土壤压实作用会加剧。因此，必须采取紧急交通控制策略，以防止或减轻机械化甘蔗作业引起的土壤压实。