Influences of Cropping Type, Mulch Materials and Preceding Radish Cropping on Root-knot Nematode Injury in Sweet Potato

Abstract

Three cropping types in sweet potato, namely, planting in April and growing with transparent polyethylene mulch, planting in May and growing with black polyethylene mulch, and planting in June and growing without mulch, were compared. The root-knot nematode density at the planting of sweet potato and the root-knot nematode injury in sweet potato were reduced by the late cropping. Then, the influences of the mulch material on the injury were examined in the same cropping season and the same nematode density. Nematode injury in sweet potato was reduced by growing with white and black double-layered polyethylene mulch and by growing without mulch as compared with the growing with transparent polyethylene mulch and with black polyethylene mulch. This suggested that the soil temperature influenced nematode injury. The cropping season of radish influenced the nematode injury in radish. However, preceding radish cropping and its season had little influence on the nematode density before succeeding sweet potato cropping and on the nematode injury in sweet potato.