Spatial and temporal electrical resistivity dynamics in a dense Ultisol under deep tillage and different citrus root-stocks

Deep tillage can be applied to face high-density soil horizons by improving the root system’s access to deeper layers. In this sense, soil and ecosystem services related to nutrients cycling and water recharge can be improved. In this study, the spatial and temporal dynamics of soil water content (θ) were inferred using two-dimensional electrical resistivity (ER) surveys, that were applied to explore the soil profile treated by deep tillage under different citrus rootstocks (RS) implantation. A seasonal scale ER monitoring (Spring 2018, Summer 2019, and Winter 2019) was carried out at a selected study area, characterized by Ultisols and located in Southeastern Brazil. Three different citrus RS-types, represented by the varieties ‘Cravo Santa Cruz lemon’ (CSC), ‘Sunki Tropical Tangerine’ (ST), and ‘Citrandarin Indio’ (CI). Deep tillage was adopted before RS citrus-types planting by opening furrows and subsoiling up to 0.6 m depth. The interrows citrus plants were covered with Brachiaria decumbens (Syn. Urochloa) in all citrus RS-type plots. A native forest area (‘Forest’) was used as reference for all θ evaluations. The model for the ER-θ relationships was determined from measurements conducted on soil samples in the laboratory. Root water uptake (RWU), in terms of θ changes, was evaluated at the different treatments under study. The obtained results proved the suitability of ER method for identifying the ER-θ dynamics in the Ultisol profiles over time. Lower and more stable θ values were obtained in the ‘Forest’ and interrow areas. Among the evaluated citrus RS-types, CSC showed the highest water use efficiency due to the greatest root system development.