Population Dynamics and Diversity of Free Living Nematodes in Sweet Potato Under Different Management Practices

Abstract

Sweet potato (Ipomoea batatas L.) is an important food crop consumed throughout Africa. This crop is associated with both plant parasitic and free-living nematodes. While plant parasitic nematodes (PPN) reduce sweet potato productivity, freeliving nematodes (FLN) play beneficial roles such as decomposition and nutrient mineralization which are essential in growth and development of the crop. Farmers use various management practices to control PPN which in turn may affect other microorganisms in the soil including the beneficial free-living nematodes. This study evaluated the impact of different farming practices on the population dynamics and diversity of free-living nematodes in sweet potato growing fields in Mwea, Kenya. Field experiments were established in a randomized complete block design involving four treatments and unamended controls during long and short rains (SR) seasons. Soil samples were collected monthly for a period of four months. Nematodes were then extracted and identified to genus level. Thirty two nematode genera belonging to four trophic groups were identified. Bacterivores were the predominant group and fungivores were the least frequent group in the two seasons. All treatments recorded high densities of bacterivorous nematodes compared to the control. Increased abundance of omnivorous and predacious nematodes was observed across the treatments in the two seasons except in the long rains season where omnivores were high in control. Goat manure was the most effective in stimulating population densities of free-living nematodes. This could be attributed to the nutritious food resources available in this amendment. Thus goat manure should be incorporated in sweet potato fields to ensure that populations of free-living nematodes are maintained or enhanced for continuous provision of the key important soil functions.