Relationship between agronomic management and nematode community structure
Abstract
A field experiment was conducted to investigate the changes in nematode community structure that are induced by agronomic management regimes. Regimes were established for a total of seven years, combining a tillage practice of conventional moldboard plowing or no-tillage with a rotation schedule of continuous corn, continuous soybean, corn-soybean, soybean-corn, corn-soybean-wheat, soybean-wheat-corn, or wheat-corn-soybean. Nematode species diversity and abundance in four replicate plots of each regime were monitored in the spring and fall of 1985 and 1986. Principal component analysis showed that factor loadings for conventional- and no-tillage practices separated on second principal components for both spring dates and on the third component for the fall of 1986. Other principal components were variables representing, either wholly or in part, the shifts in species abundance occurring with crop rotation. Diversity between contrasting tillage practices was assessed by analyzing species richness in samples. Plant-feeding nematodes were more diverse with conventional tillage in the fall, whereas fungivores in the fall were more diverse with no-tillage. Bacterivores were more diverse with no-tillage in both the spring and fall. Omnivore species richness was unaffected by tillage practices. Rotation schedules were interpreted as the positions on a cropping gradient. Nematode communities were structured on a corn cropping gradient in a sequential progression of species. Species continuums on corn and soybean gradients were corroborated by negative associations of community similarity and gradient position that were more frequent than would be expected with random variation. Regression analysis showed similarity and position were more strongly related with conventional tillage on a corn gradient and with no-tillage on a soybean gradient. Analysis of variance showed the absolute abundances of fungivore, bacterivore, and omnivore trophic groups were less with corn than with wheat in 1985, while in 1986, the abundances of fungivores and omnivores were less with corn than with soybean. The plant-feeding trophic group did not respond to rotation schedules as a factor influencing abundance.
Degree
Ph.D.
Advisors
Ferris, Purdue University.
Subject Area
Ecology|Entomology|Agronomy
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