Solarization of spent potting media in plastic bags and organic amendments for the production of bedding plants

An experiment was conducted to evaluate the effectiveness of solarization of spent potting media and the addition of organic amendments on bedding plants production in southern Florida. Spent potting media in clear, 0.1-mm-thick polyethylene plastic bags were solarized for 0, 2 or 4 weeks. Solarized media were compared to new potting media. In addition, each treatment was compared to humic acid treated media that were arranged in a completely randomized experimental design with eight replications. Impatiens, periwinkle and petunia were grown in each of these treatments and evaluated for their horticultural parameters 9 weeks after transplanting. Solarization of spent media for 2 or 4 weeks increased plant height, width, plant dry weight, and flower number per plant compared with those grown in non-solarized media, irrespective of the organic amendment. Solarization for 2 or 4 weeks doubled the values of the horticultural parameters in impatiens and periwinkle plants compared with those grown in new or non-solarized media. All horticultural parameters values of petunia plants that were grown in solarized media for 2 or 4 weeks and received humic acid were comparable with those grown in new media. The addition of humic acid significantly increased petunia plant width, dry weight, and number of flowers in 2 or 4 weeks solarized media and the latter two parameters in new media. Solarization of recycled media for 2 or 4 weeks in plastic bags has a high potential to be considered as a useful soil disinfectant, and is an inexpensive, fast, and effective technique for recycling stockpiled disease-infected media and providing horticultural parameter values for impatiens and petunia comparable with plants grown in new potting media. Combining solarization and humic acid for petunia can attain even higher horticultural values. The use of this solarization technique as an environmentally safe media disinfectant with organic amendments offers an additional option for increasing pest control and crop yield of bedding plants, an opportunity to reduce input to landfills, and has a great potential to be adopted by nursery growers and homeowners.