The border effect of soil solarization

Abstract A gradient of reduced effectiveness of solarization toward the edge of the plastic mulch is known as a ‘border effect’, corresponding with decreasing soil temperatures from the middle toward the edge of the mulched area. The cyst nematode Heterodera avenae , of wheat was completely controlled by solarization at 90 cm or more inward from the edge of the mulched plots. A gradient of decreasing effectiveness of nematode control in the mulched plot, toward the edge of the mulch, was observed. There was a similar gradient with height of wheat planted after solarization, and in the incidence of pod wart disease of peanuts caused by Streptomyces spp., planted as a second crop after soil disinfestation. Disease reduction was correlated with a decrease in population of streptomycetes. A similar, but less pronounced, border effect was observed when solarization was combined with methyl bromide or formalin at reduced dosages.