Heat-retentive films for increasing soil temperatures during solarization in a humid, cloudy environment

Although summer soil solarization is a viable technique for the control of soilborne pests, periods of cloudy skies and high rainfall typical of the southeastern United States limit the heating of soils. This study was devised to evaluate whether polyethylene films designed for improved heat conservation could increase soil solarization temperatures under humid environmental conditions. Soil solarization was conducted in Summer 1996 at Quincy, Gainesville, and Bradenton: located in north, north central, and west central Florida, respectively. Temperatures at soil depths of 5, 10, and 25 cm were higher under clear solarization films than under black polyethylene. A clear, thermal-infrared absorbing film (TIR) was consistently more effective in increasing soil temperature than was a double-layered, clear bubble film or a 30 mu m clear, low-density polyethylene film. Soil temperatures under all film types were reduced by rainfall, but remained highest under TIR film. On cloudly days with light rainfall, temperatures under TIR film exceeded 45 degrees C at 5 cm depth. Soil temperatures rose rapidly,when rainy weather was followed by a clear day. Cumulative exposure to temperatures greater than or equal to 45 and 50 degrees C was greater with the TIR film than with the other films, indicating that it has the greatest potential for soil solarization in humid climates.