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Relation of Within-Field Spatial Variation of Plant-Parasitic Nematode Population Densities and Edaphic Factors. J. P. Noe, Research associate, Department of Plant Pathology, North Carolina State University, Raleigh 27650; K. R. Barker, Professor, Department of Plant Pathology, North Carolina State University, Raleigh 27650. Phytopathology 75:247-252. Accepted for publication 12 September 1984. Copyright 1985 The American Phytopathological Society. DOI: 10.1094/Phyto-75-247.

Variations among total nematode population densities, and overwinter changes in population densities of Meloidogyne incognita, Tylenchor-hynchus claytoni and Helicotylenchus dihystera, were related to soil parameters in 64 1-m2 contiguous quadrats at two sites. Discriminant functions composed of 26 edaphic variables correctly classified 70% of the quadrats into high, medium, and low categories of nematode density. Optimum discrimination was provided by six to eight soil parameters in stepwise-discriminant analyses. Different subsets of the 26 edaphic variables were useful with different species and sites for the discrimination of quadrats according to nematode densities. Quadrats were separated into clusters of high, medium, and low nematode densities along edaphic canonical axes. Variation in soil parameters accounted for over 50% of the spatial variation in nematode counts. Clay content and sodium and copper concentrations were particularly useful in explaining spatial variation among population densities of M. incognita, T. claytoni, and H. dihystera.

Additional keywords: nematode ecology, spatial distribution.