The determination of the spatial distribution of soil moisture in the field is relevant for many purposes in agriculture and engineering, but it is still a challenge, since standard determination methods have limitations and problems of representativeness. Electrical resistivity may be used with this finality, but this method is still poorly studied for highly weathered tropical soils, which present structural and textural peculiarities. This work aims to present the calibration of the moisture/electrical resistivity relationships for a typical tropical soil, and to evaluate its robustness as a soil moisture prediction method. A highly weathered clay soil (Oxisol), representative of the Brazilian savanna (“Cerrado”), was sampled and the resistivity tests of the A, B_w and C horizons were conducted in a four-electrode cell array. The A and B_w horizons of clay Oxisols usually present resistivity values greater than temperate soils counterparts, which can be attributed to the lower content of highly active clays and higher macroporosity. The soil electrical resistivity/volumetric moisture relationship present a nonlinear and inverse trend and the generalized form of Archie's law has the potential to be applied to determine the water content of these soils. The electrical resistivity/volumetric soil moisture semi-log plot showed a two-step pattern, with a remarkable change in the behavior around the moisture associated to the wilting point. The field validation shows that the use of the electrical resistivity is possible for the measurement of soil moisture and for the subsurface mapping of its horizons.

田间土壤水分空间分布的确定与农业和工程领域的许多目的有关，但由于标准的确定方法存在局限性和代表性问题，这仍然是一个挑战。电阻率可以用于这种最终结果，但是对于高度风化的热带土壤，这种方法的研究仍然很少，因为这些土壤具有结构和质地特性。这项工作旨在展示典型热带土壤的水分/电阻率关系的校准，并评估其作为土壤水分预测方法的稳健性。对代表巴西稀树草原（“Cerrado”）的高度风化粘土（Oxisol）进行采样，并对 A、B _w的电阻率测试和 C 层在四电极单元阵列中进行。A 和 B _w粘土氧化溶胶的电阻率值通常高于温带土壤对应物，这可归因于高活性粘土含量较低和大孔隙率较高。土壤电阻率/体积水分关系呈现非线性和反向趋势，阿奇定律的广义形式有可能用于确定这些土壤的含水量。电阻率/体积土壤水分半对数图显示出两步模式，与萎蔫点相关的水分周围的行为发生了显着变化。现场验证表明，电阻率可以用于测量土壤湿度和地层地下测绘。