Nematicidal effects of decomposing plant amendments have long been known, and many different crops have been shown to suppress a range of species of plant parasitic nematodes. Leguminous winter cover crops such as hairy vetch (Vicia villosa Roth.) and crimson clover (Trifolium incarnatum L.) have varying degrees of tolerance to high populations of certain plant parasitic nematodes, but their ability to suppress populations have not been well studied. The objective of this study was to examine the effectiveness of commonly-used winter cover crops to suppress populations of root-knot (Meloidogyne arenaria) and reniform (Rotylenchulus reniformis) nematodes in field and greenhouse studies. Common vetch (Vicia sativa L. cv. 'Cahaba White'), hairy vetch and crimson clover were planted in autumn, each at the rate of 22 kg ha(-1). Two additional treatments were bare soil (no cover crop) and bare soil plus nitrogen added at a rate equal to the average N content of the incorporated cover crops. Cover crops were incorporated just before planting okra (Abelmoschus esculentus L. Moench). Few significant differences in nematode populations were noted at any sampling date because of cover crop treatments. When differences occurred, populations of M. arenaria were lower in bare soil treatments in comparison with those with an incorporated cover crop. Okra yield was unaffected by any cover crop. In the greenhouse study, R. reniformis populations were reduced in rye and bare soil treatments, but populations were unaffected in common or hairy vetch treatments. (C) 1998 Elsevier Science B.V. All rights reserved.
