This study was designed to measure the variation of precompression stress (σ_p) with initial bulk density and initial water content and to propose pedo-transfer functions to estimate σ_p for two Brazilian no-till Oxisols. Undisturbed soil cores were randomly sampled (to obtain an as large as possible variation in bulk density) from two soils with 22 and 32% clay, equilibrated at matric suctions of 10, 30, 60, 100, 330, 1000, 1500 and 3000 hPa and subjected to uniaxial compression tests. For each compression curve, σ_p was calculated and regressions models and correlation analyses were used to examine the σ_p, bulk density and water content relationships. The σ_p showed a significant correlation with initial bulk density and initial water content for the soil with 22% clay. For the soil with 32% of clay, the σ_p significantly decreased with the water content, but the relation was considerably poor with initial bulk density. Overall, the results revealed that the effect of soil water content and bulk density on σ_p increases or decreases with increasing clay content, respectively. Models for soils with higher clay content may explain much of the variability of σ_p only as a function of water content, while for sandy soils bulk density should also be considered.

本研究设计为测量预压应力（σ的变化_p）与初始的堆积密度和初始水含量，并提出小儿传递函数来估计σ _p为2巴西免耕氧化土。从两种含22％和32％黏土的土壤中随机采样未扰动的土壤核心（以获得尽可能大的堆积密度变化），在10、30、60、100、330、1000、1500和3000 hPa的吸力下平衡并进行了单轴压缩测试。对于每条压缩曲线，计算_σp，并使用回归模型和相关分析检查_σp，堆积密度和含水量之间的关系。该σ _p结果表明，粘土含量为22％的土壤与初始容重和初始含水量显着相关。对于粘土含量为32％的土壤，_σp随着含水量的增加而显着下降，但与初始堆积密度的关系却很差。总体而言，结果表明，土壤含水量和堆积密度对_σp的影响分别随粘土含量的增加而增加或减少。具有较高粘土含量的土壤模型可能仅解释了_σp随水含量变化的大部分变化，而对于沙质土壤，还应考虑体积密度。