Estimating grapevine-relevant physicochemical soil zones using apparent electrical conductivity and in-phase data from EMI methods

This study explores the ability of the frequency domain electromagnetic induction (EMI) method to produce physicochemical soil maps with relevance to grapevine vigor. The study was conducted in the Me ' doc area of the Bordeaux wine region in France. A flexible clustering approach was used with both the apparent electrical conductivity and the in-phase components of EMI measurements. Soil zones with distinct physicochemical sig-natures were successfully identified, primarily due to the inclusion of in-phase data in the clustering method. Importantly, this approach does not use prior information to guide zone classification and does not require calibration of EMI measurements. Extensive soil texture and physicochemical measurements were used to compare the different zones identified by the clustering approach. Grapevine vigor was assessed using normalized vegetation index (NDVI) data to help conceptualize the critical physicochemical variables of the soil. It was evident that NDVI and EMI data were correlated to organic matter, nitrogen, CEC, pH, CaO, and copper concentration in one of the investigated sites. Unlike previous work in other Bordeaux soil viticulture areas, soil texture at these sites was relatively homogenous and consequently did not influence plant vigor substantially. This work demonstrates the value of the in-phase component of EMI measurements to estimate soil zonation. More generally, this work demonstrates the ability of coupled EMI and NDVI surveys to inform viticulture at scales relevant to management decisions.