Geostatistical modeling of the spatial variability and risk areas of southern root-knot nematodes in relation to soil properties

Abstract

Identifying the spatial variability and risk areas for southern root-knot nematode [Meloidogyne incognita (Kofoid & White) Chitwood] (RKN) is key for site-specific management (SSM) of cotton (Gossypium hirsutum L.) fields. The objectives of this study were to: (i) determine the soil properties that influence RKN occurrence at different scales; and (ii) delineate risk areas of RKN by indicator kriging. The study site was a cotton field located in the southeastern coastal plain region of the USA. Nested semivariograms indicated that RKN samples, collected from a 50×50 m grid, exhibited a local and regional scale of variation describing small and large clusters of RKN population density. Factorial kriging decomposed RKN and soil properties variability into different spatial components. Scale dependent correlations between RKN data showed that the areas with high RKN population remained stable though the growing season. RKN data were strongly correlated with slope (SL) at local scale and with apparent soil electrical conductivity deep (EC a-d ) at both local and regional scales, which illustrate the potential of these soil physical properties as surrogate data for RKN population. The correlation between RKN data and soil chemical properties was soil texture mediated. Indicator kriging (IK) maps developed using either RKN, the relation between RKN and soil electrical conductivity or a combination of both, depicted the probability for RKN population to exceed the threshold of 100 second stage juveniles/100 cm 3 of soil. Incorporating EC a-d as soft data improved predictions favoring the reduction of the number of RKN observations required to map areas at risk for high RKN population.

Spatial Variability Modeling of Soil Erodibility Index in Relation to Some Soil Properties at Field Scale

“…2; soil porosity. A dataset is considered to be normally distributed when skewness coefficients are between -1 to 1 (Virgilio et al, 2007;Ortiz et al, 2010). Since all the dataset were normally distributed there was no need for data transformation.…”

Distribuição espacial de Pratylenchus brachyurus em área de soja no Leste do Maranhão

“…Entretanto, com a implantação da monocultura da soja na região Leste do estado do Maranhão, a população de P. brachyurus vem aumentando muito no solo e causando perdas significativas de produtividade na cultura. As características físicas do solo são importantes fatores que influenciam a distribuição de nematoides (Ortiz et al, 2010;Vicente et al, 2015). Dantas et al (2014), avaliando a relação solo-paisagem na mesma região e tipo de solo, concluíram que pedoformas convexas, semelhante a forma da área estudada neste trabalho, apresentam alta macroporosidade e baixa densidade e resistência do solo à penetração, características que facilitam a migração do P. brachyurus no solo (Vicente et al, 2015) e potencializam o efeito de disseminação causado pelo preparo mecanizado do solo.…”

Relationship between soil organic matter and nematodes in sugarcane fields

“…Thus, in order to obtain information on the dynamics of nematode communities in the soil, adequate sampling and data analysis procedures are required (PINHEIRO et al, 2008). Geostatistical mapping allows visualizing the variability pattern of these organisms, constituting a useful tool for defining management strategies and recovery of infested areas (ORTIZ et al, 2010). However, studies on the spatial nematode distribution are incipient but relevant for the development of sampling plans aiming at the application in integrated pest management programs.…”