Electrical Resistivity Tomography (ERT) of Immature Oil Palm Roots and Its Implication on Peanuts Growth and Yield in Intercropping for Sustainable Agriculture

Abstract

This study aimed to determine the root distribution of three-year-old oil palms and the morphological characteristics of annual food crops grown under intercropping and monoculture systems. The research was conducted in Batu Penyu Village, East Belitung, using a single-factor Randomized Complete Block Design (RCBD) with three replications. The tested factor was the cropping system (intercropping vs. monoculture), with peanuts as the intercropped food crop. Oil palm root distribution was mapped non-destructively using electrical resistivity geoelectrical methods, while food crop root morphology was assessed destructively. Data were analyzed using Analysis of Variance (ANOVA), followed by a Least Significant Difference (LSD) test at a 5% significance level. 2D mapping of the oil palm root zone was processed using RES2DINV software. The results indicated that the root systems of three-year-old oil palms are dominated by primary and secondary roots, with minor contributions from tertiary and quaternary roots. These roots spread horizontally 1.5 – 2.5 m from the trunk at a depth of < 30 cm. This spatial arrangement suggests a lack of root zone competition between the oil palms and the intercropped food crops, as each species occupies distinct soil spaces. Furthermore, the root morphology of peanuts grown in the intercropping system was identical to those in monoculture, indicating that the growth and yield of intercropped peanuts are not inhibited by the presence of young oil palm roots.