The border effect of soil solarization

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.