Roots play an important role in plants and are responsible for several functions; among them are anchorage and nutrient and water absorption. Several methodologies are being tested and used to study plant root systems in order to avoid destructive root sampling. Electrical resistivity tomography is among these methodologies. The aim of this preliminary study was to use electrical resistivity for detecting root biomass in coffee trees. Measurements were performed in a soil transect with an ABM AL 48-b resistivimeter with a pole-dipole configuration. The tomograms indicated variability in soil resistivity values ranging from 120 to 1400？？·m？1. At the first 0.30？cm soil layer, these values were between 267 and 952？？·m？1. Oriented by this result, root samples were taken at 0.10, 0.20, and 0.30？m depths within 0.50？m intervals along the soil transect to compare soil resistivity with root mass density (RMD). RMD data, up to this depth, varied from 0.000019 to 0.009469？Mg·m？3, showing high spatial variability and significant relationship to the observed values of soil resistivity. These preliminary results showed that the electrical resistivity tomography can contribute to root biomass studies in coffee plants; however, more experiments are necessary to confirm the found results in Brazil coffee plantations. 1. Introduction Roots play an important role in plants and are responsible for several functions, which include anchorage, acquisition of soil-based resources, storage, synthesis of growth substances, source of organic materials, propagation, and others [1]. Root research under natural conditions is very labor intensive and time consuming. Several methods related to root studies were described in the literature, and these include destructive and nondestructive sampling [2]. Among them one can cite excavation, monolith, auger, profile wall, container, and others [2, 3]. Most of them are destructive, which prevents future measurements at same location, and require separation of the roots from the soil, commonly by washing. Other more sophisticated methodologies, classified as nondestructive sampling, involve root studies using glass wall, rhizotrons, minirhizotrons [4], and video and digital cameras [2]. In this case, image analysis helps to evaluate roots behavior and allows the researcher to return to the same location for new data collection. New high technologies of root research can also help avoid destructive sampling and allowing an intensive root study in a new way. Several methodologies were tested such as ground-penetrating radar [5–8], X-ray
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