Effect of field establishment methods on root-knot nematode ( Meloidogyne spp.) infection and growth of Sesbania sesban in western Kenya

Abstract

Pot studies indicated that root-knot nematode ( Meloidogyne javanica) infection reduces sesbania ( Sesbania sesban) growth and planting methods modify the nematode damage, but their effects on sesbania biomass production at the field scale are not known. A field study was conducted in western Kenya for 2 yr, comparing direct seeding of sesbania with transplanting of bare-rooted seedlings in pure stands, with and without nematicide application in the field and in the nursery. In moist conditions, neither planting method nor nematicide had any influence on seedling survival and early growth. When early season rainfall was low and erratic, transplanted seedlings survived and grew better than seedlings from direct sowing, and nematicide application in the field and/or nursery improved seedling survival. Direct seeded sesbania had significantly less nematode galling and smaller nematode populations in the roots than transplanted sesbania. Both the establishment methods produced similar quantities of biomass, but direct seeded sesbania produced significantly greater biomass than the transplanted crop, if seedlings were already infected with nematodes in the nursery. Nematode infection on average reduced total sesbania biomass by 19%. Where sesbania cover crops have to be established by transplanting for socio-economic reasons, it is essential to use healthy seedlings free from nematodes for a good plant stand and early growth. Nematode-free seedlings can be produced on farms by at least one month of solarization of seedbeds. Neither field establishment method, nor nematicide application altered the soil nematode populations over a 12-month period. This means that the potential threat of increased Meloidogyne populations to nematode-susceptible crops following sesbania cover crops remains the same irrespective of how sesbania is established.