Effect of plant bed type on nematode density and yield of cabbage in two regions of Ghana

Cole crop production in general and cabbage in particular is constrained by pest infestation, reducing the farmer’s profit margin considerably. In this study, the effects of three plant bed types: flat, ridges and raised beds were investigated in 2012 and 2013 at Asiwa and Dormaa Ahenkro in Ghana, respectively to study their effects on plant parasitic nematodes and the yield of cabbage. Treatment effects on nematode density/200 cm3 soil, nematode density/5 cm3 cabbage root, root galling, cabbage heads, yield and leaf width were investigated. Flat bed treatment resulted in significant (P < 0.05) nematode reduction (84 and 67%) of Meloidogyne spp. and Helicotylenchus multicintus, respectively, at Asiwa compared to ridged bed treatment. At Dormaa Ahenkro, however, flat bed treatment resulted in significant reduction (81, 62, 97 and 98%) of Meloidogyne spp., Pratylenchus penetrans, H. multicintus and Rotylenchulus reniformis, respectively. Also, flat bed treatment resulted in 24 and 16% more cabbage heads compared to ridged and raised bed treatments at Asiwa and 44 and 17% more than ridged and raised bed treatments at Dormaa Ahenkro, respectively. Yield differences among treatments were however found to be not significant. The weakness in the experiment was that instead of using yield /unit area in determining the potential yield of the respective treatments, the weight of 10 heads of cabbage/treatment was used.  Ridged bed treatment cabbage leaves were 0.5 and 0.2 times broader than flat bed treatment cabbage at Asiwa and Dormaa Ahenkro, respectively. The adoption of Oxylus variety, a poor host of root-knot nematode and flat method of planting, could sustain very well the cabbage industry in Ghana.   Key words: Brassica oleracea, cole crops, Ghana, plant parasitic nematodes, plant bed.