Submitted to: Proceedings of Florida State Horticultural Society
Publication Type: Proceedings
Publication Acceptance Date: 8/9/2006
Publication Date: 10/16/2005
Citation: Wang, Q.R., Klassen, W., Li, Y., Handoo, Z.A., Olczyk, T., Codallo, M. 2005. Influence of cover crops in rotation on improving okra (abelmoschus esculentus l.) yield and suppressing parasitic nematodes. Proceedings of Florida State Horticultural Society. 118:177-183. Interpretive Summary: Plant-parasitic nematodes are microscopic worms that cause an estimated ten-billion-dollar crop loss in the United States each year. These losses will increase because the most widely used chemical pesticide used to kill soil nematodes will soon be prohibited from use. One approach to solving the problem of designing new, safe means of controlling nematodes is through the use of cover crops. Cover crops are plants that nematodes will not infect; these plants can be grown to potentially reduce nematode numbers in soil. Therefore, in the present study, ARS and University of Florida scientists evaluated four different cover crops in field and pot experiments to determine if the cover crops could reduce population levels of the root-knot nematode, the most economically important nematode infecting vegetables in the United States. The cover crops were sunn hemp, cowpea, velvetbean and sorghum sudangrass, and the vegetable evaluated was okra. The scientists discovered that each cover crop, especially sunn hemp and velvetbean, stimulated okra yield and suppressed root-knot and other plant-parasitic nematodes. These results are significant because these nematode-resistant cover crops may be promising candidates as replacements for chemical nematicides in some okra production systems. This research will be used by scientists developing new methods for safely controlling nematode-induced crop losses
Technical Abstract: The influence of growing and incorporating summer cover crops on subsequent vegetable crop production and on population densities of the root-knot nematode (Meloidogyne incognita) was investigated in field and pot experiments at Homestead, Florida. The cover crops utilized in the field and pot experiments were sunn hemp (Crotalaria juncea), cowpea (Vigna unguiculata), velvetbean (Mucuna deeringiana) and sorghum sudangrass (sorghum bicolor x S. bicolor var. Sudanese). A nematode susceptible vegetable crop, okra (Abelmoschus esculentus) was grown in rotation with the cover crops. The results indicated that all four cover crops improved subsequent okra yields, especially sunn hemp and velvetbean, which produced large amounts of biomass with high contents of nitrogen (N). Okra fruit yields increased by 33% and 11% in velvetbean and sunn hemp treatments in the field, compared to that in the sorghum sudangrass treatment, the conventional cover crop treatment in this area. In crop rotation studies conducted in pots, okra fruit yields were increased by 3.6, 3.1, and 1.5 times by rotation with sunn hemp, velvetbean and cowpea, respectively, compared to yields of okra following okra. Populations of root-knot nematodes were substantially suppressed by sunn hemp, cowpea and velvetbean, and this suppression was especially strong by sunn hemp. Moreover, the root-knot nematode suppressive effect of sunn hemp persisted to protect a subsequent okra crop. The results indicate that rotating the summer cover crops sunn hemp or velvetbean with okra can significantly improve okra yields in addition to suppressing root-knot nematodes.