Spatial Variability of Root Knot Nematodes in Relation to Within Field Variability of Soil Properties

摘要

Site-specific management (SSM) of cotton (Gossypium hirsutum L) fields under risk of southern root-knot nematode [M. incognita] (RKN) infection may offer producers better management of on-farm resources and optimization of profitability. However, it requires the study of RKN spatio-temporal variability and the identification of surrogate data spatially correlated with its occurrence. The objectives of this study were (i) determine the magnitude, extent, and changes through time on the spatial variability of RKN at the field scale, (ii) establish the relationship between RKN occurrence and the spatial variability of soil physical and chemical properties, and (Hi) delineate areas at risk for RKN based on surrogate data. The spatial relations between soil physical properties (soil electrical conductivity - EC_a, slope, and elevation) and soil chemical properties (P, K, Ca, Mg, and soil pH) on RKN population density were studied in two cotton fields planted in southern Georgia, USA, in 2006. The spatio-temporal variability of the RKN was studied through semivariograms. The spatial correlation between RKN and soil properties was studied through canonical correlation and cross-correlograms. Soil properties highly correlated with RKN population density were entered into an ordinary logistic regression model to create a map of probability risk for RKN population density over a specific threshold value. The aggregated pattern of the RKN facilitated the segregation of RKN risk areas based on low values ofEC_a.