Let the Power of the Sun Restore Your Garden Soil
Written by Philippe Bilger, Master Gardener Volunteer
For many living in South Florida, summer is the time to enjoy the sun and the fun activities available to us. Due to the heat and humidity during the summer, growing a traditional vegetable garden can be difficult, so why not use this time to give your garden a rest and prepare it for the following growing season in the fall.
Part of the preparation can be to use the power of the sun to enhance the condition of the soil through solarization. What is soil solarization? Soil solarization is a soil preparation practice that helps manage those pesky weeds and possibly control nematodes, insects, and diseases common in our soils.1 It involves covering the soil with clear plastic sheets to raise the soil temperature. Residents that have vegetable gardens in open areas or raised beds can use this simple technique. I have used the solarization for several years; it has proven effective in reducing the emergence of weeds, and nematodes have not been a problem in my vegetable garden.
According to the University of Florida’s Institute of Food and Agricultural Sciences, trials have shown that if there is sufficient sun to maintain elevated soil temperatures, this practice helps manage garden weeds, pests, and diseases for three to four months. The goal is to reach a minimum temperature of 40C (104F). Obviously, higher temperatures will take less time and be more effective. Solarization is most efficacious for treating the top four to six inches of soil. To maximize the effects of the sun, it is best done during the months of June, July, and August.
At the end of the growing season, begin by clearing the bed of any remaining vegetables and remove all weeds and debris until you have a clean and clear soil surface. Soil amendments containing organic matter, such as compost, potting soil, and peat moss can be added at this time. In order to avoid the accumulation of water, mound the surface slightly with the crest in the middle. For good contact with the plastic, smooth and level the soil, while maintaining the slight mound in the middle. This allows the water to run off to the sides. Moisten the soil well and allow the bed to sit overnight.
It is best to use thin clear plastic that lasts for at least 6 weeks, holds up in the sun, and does not puncture easily. Black, translucent, and opaque plastics are not suitable because they do not let sufficient light thru to heat the soil. Cut the sheet larger than the area to be covered, then adapt and stretch the plastic snug against the soil. Bury the edges into the soil to hold the plastic down and not allow heat to escape. Allow the soil to bake for a minimum of six weeks or longer. I prefer three months in my garden. When it comes time to plant, simply remove the plastic and make final preparations for the garden.
Though it involves some work and sweat equity, soil solarization is a convenient practice to reduce annoying weeds and the need for harmful chemicals. In addition, it helps decompose organic matter to improve the soil profile and availability of nutrients. The garden takes a rest to rebuild and restore. There is an added benefit; it gives us time to enjoy the summer and prepare for next season!
1. Robert McSorley and Harsimran K. Gill. 2009. Introduction to Soil Solarization. ENY-602 Gainesville: University of Florida Institute of Food and Agricultural Sciences. http://edis.ifas.ufl.edu/pdffiles/IN/IN85600.pdf
2. University of Florida Institute of Food and Agricultural Sciences, Gardening Solutions. July 2017. Soil Solarization. https://gardeningsolutions.ifas.ufl.edu
3. Krueger, R., and R. McSorley. 2009. Solarization for Pest Management in Florida. ENY-902. Gainesville: University of Florida Institute of Food and Agricultural Sciences. http://edis.ifas.ufl.edu/in824