Assessment of Soil Water Content Variability Using Electrical Resistivity Imaging in an Oxisol under Conservation Cropping Systems

Agricultural systems are increasingly challenged of achieving high yields while optimizing plant water consumption. Soil conservation practices are preponderant in rain-fed agriculture for increasing water infiltration, water storage in the soil, and for promoting root development. This study aimed to assess the spatial-temporal soil water content (θ) dynamics identified by the application of electrical resistivity tomography (ERT) surveys in an Oxisol under grain production systems in the Brazilian Cerrado. The utilized cropping systems were: soybean monoculture (SS); maize monoculture (MM); maize/soybean rotation (MS); maize/soybean rotation with intercropped brachiaria (MBSB); maize/soybean rotation with high fertilizer investment (MS-HI), and MBSB and high fertilizer investment (MBSB-HI). ERT measurements were performed at field conditions using different time-steps during the rainy (March, 2019) and dry seasons (July 2018 and 2019). Logarithmic and power models were tested for evaluating the relationships between θ and the electrical resistivity (ρ). Results showed ERT was adequate for monitoring the spatial-temporal θ variation and for inferring soil-plant related processes (i.e., water uptake and macro-porosity due to roots development). The power model was more suitable in depicting the θ - ρ relationship, and for imaging the water unavailability for plants during the dry periods. Intercropped brachiaria positively affected the θ dynamics due to its aggressive root systems. MBSB-HI showed the highest θ values in the rainy season, demonstrating that ecological intensified cropping systems can help overcome severe dry spells, in the Brazilian Cerrado.