Plastic is laid over a soil bed generally 4-6 inches high and 30 inches wide, with a slope of 1.25 inches from the center to the edge. The raised bed will warm up the soil quicker in the spring and also will shed excess water off the bed into the middle, thus keeping the crop drier and preventing deterioration in quality of the product. The color of a mulch determines its energy-radiating behavior and its influence on the microclimate around the plant.
Color affects the surface temperature of the mulch and the underlying soil temperature.
Black is the most commonly used color of polyethylene mulch. Soil temperatures under black plastic mulch during the daytime are generally 5 F higher at a 2 inch depth and 3 F higher at a 4 inch depth compared to that of bare soil. Daytime soil temperatures under clear plastic mulch during the daytime are generally 8 to 14 F higher at a 2 inch depth and 6 to 9 F higher at a 4 inch depth compared to that of bare soil. However, the use of clear plastic mulch requires the use of a herbicide or fumigant to control weeds. By raising the soil temperature in the planting bed, plant growth is accelerated, producing earlier yields.