Plant parasitic nematodes have been identified among the major pests in many banana ( Musa spp, L.) growing areas. However, soil free-living nematodes contribute to key biological processes and can serve as indicators of soil health. This study investigated the structure and diversity of soil nematode communities in relation to soil physico-chemical properties in Grevillea robusta –banana farming systems across three agroecological zones of Kirinyaga County, Central Kenya, during both the rainy and dry seasons. Significantly higher soil potassium, magnesium, calcium, phosphorus, bulk density and pH were found in soils under sole crop banana compared to G. robusta -banana intercrops and G. robusta sole crop. The density of herbivore nematodes was significantly higher in sole crop banana at 233 individuals 200 cm −3 compared to G. robusta sole crop (53 individuals 200 cm −3 ) and G. robusta -banana intercrops (96 individuals 200 cm −3 ) in all the agroecological zones. The overall nematode density as well as that of all the nematode trophic groups increased significantly during the rainy season compared to the dry season. The G. robusta -banana intercrops and G. robusta sole crop supported a diverse and evenly distributed nematode community compared to sole crop banana. These results suggest that intercropping banana with G. robusta trees increases the belowground competition for soil nutrients. However, this practice seems more sustainable than growing banana in monoculture since G. robusta -banana intercrops maintained a healthy soil whereas the banana monoculture favoured the build-up of parasitic nematodes.
Musongora et al. (Sun,) studied this question.