Are community structures of soil nematodes different between organic and conventional farming systems in commercial tomato fields?

Abstract

Compared with studies conducted in experimental crop fields, those in commercial fields have been very limited\rto examining how organic (ORG) and conventional (CONV) farming systems differ in their effects on biological and\rphysicochemical characteristics of soils. To evaluate practical effects of ORG systems, a comparison is essential\rwith “practical” CONV systems where organic amendments are also used in addition to chemical fertilizers and pesticides.\rWe compared nematode community structures between the two systems for commercial tomato production\rin greenhouses located in northern Japan in 2005 and 2006. We examined if the farming system was still influential\reven when differences in soil texture, study plot locations and growing seasons among the plots were considered.\rThe density of the predator-omnivore group, with Dorylaimida as the dominant taxon, and Structure Index were\ralways significantly affected by farming system, and their values were greater in ORG. Redundancy analysis in\r2005 revealed that farming system could significantly explain the whole community structure, and determined\rDorylaimida as an indicator for ORG, while Diplogasteridae and Anguinidae were indicators for CONV. Although\rredundancy analysis could not significantly explain community structure with farming system in 2006, Dorylaimida\rand Diplogasteridae were still good indicators for the two systems. Individual variables, such as soil texture and\rbacterial density, were found to have significant effects on the two nematode taxa, although we could not interpret\rsufficiently the causal relationships. Further studies should include other measurements such as chemical pesticides\rapplied for better interpretation of the differences between these systems. Nematol. Res. 39 (2), 63-71 (2009).\rKey words : predator-omnivore group, Structure Index.