Recycling used container media with solarization^©

INTRODUCTION
Underutilization of used potting media for crop production in environmental horticulture wastes money and resources. In conversations with growers, it is estimated that about 10% of plants with potting media are culled and disposed of in the industry. Many nurseries dump culled plants and media on site and this waste is generally not reused. In an effort to recycle this waste, a series of methods were tested to solarize the used potting media. Solarization is a sustainable, inexpensive, and effective method to reduce pathogens, nematodes, and weeds. Solarization works using the light energy of the sun and transforming it into heat. When temperatures reach a certain threshold over a certain critical time, pests can be eliminated. Different pests (i.e., weed seeds, insects, fungi) have different thresholds for being heat killed. Research has shown that if container medium is held at temperatures of 70°C (158°F) or higher for 30 min or 60°C (140°F) or higher for 1 h, solarization can completely eliminate plant pests (Stapleton et al., 2008). Methods have been developed for treating smaller quantities of medium such as in nursery pots on pallets with a “double tent” method (Stapleton, 2000). Research has shown the effective use of solarization to treat small bags of potting soil on benches (Zinati et al., 2002). What was lacking was a larger scale method to treat higher quantities of spent potting media.