Application of soil solarization to control root-knot nematodes and weeds in transplanted tomato

The effects of 0, 10, 20 and 30 days of tightly covering of tomato beds with thick (50 mm) transparent polyethylene plastic sheet prior to transplanting were assessed on soil temperatures, root-knot nematodes, specific weeds, and growth and fruit yield of tomato in a field experiment at the Teaching and Research Farm of the University of Cape Coast in 1992. Mean soil temperatures ranged from 44 to 53 oC at 5 cm depth and from36 to 46 oC at 10 cm depth with temperatures increasing with successive increases in period of solarization. Soil nematodes, mostly root-knot (Meloidogyne spp.) were significantly reduced and the longer the period of solarization the greater was the reduction. Root-galling incidence in tomato was likewise reduced significantly by solarization. Annual weed species which reproduce by means of numerous tiny seeds, including Boerhavia diffusa, Ageratum conyzoides, Euphorbia heterophylla and Tridax procumbense, were effectively controlled particularly by long periods of solarization. On the other hand, Cynodon dactylon which reproduces vegetatively by stolons was partially controlled. The predominant weed species Cyperus rotundus, a perennial, could not be controlled even by the longest period of solarization. Soil solarization also improved crop height and fruit yield. This is attributed possibly to its lethal effect on nematodes, weeds and its favourable influence on mineralization of soil organic matter, and reduction in fruit decay incidence. (Ghana Journal of Agricultural Science, 1996, 29(2): 91-98