soil preparation | Gardening in the Panhandle

Now is Time to Use Solar Power Against Soil Pests

by Mark Tancig | Jul 9, 2020

North Florida vegetable gardeners have made it to summer and now the plants and gardeners are starting to give in to the heat and humidity. The squash has likely succumbed to squash vine borers, many of the tomato varieties are having trouble setting fruit, stink bugs are all over, and gardeners easily wilt by noon. This is a good time to use our oppressive heat to your advantage in the vegetable garden by solarizing the soil.

We have reached the peak of heat. Use it to your advantage in the garden. Source: National Weather Service.

Soil solarization is a method of pest control that creates a greenhouse to heat up the soil in an effort to drive away pests. Pests that can be reduced with soil solarization include weeds, various soil-borne fungal pathogens, and nematodes. Weed seeds can actually be killed by the increased temperatures, sometimes as high as 140 degrees Fahrenheit, while fungi and nematodes are merely driven deeper into the soil layer as they try to escape the heat. Although they are not killed, this can help vegetable gardeners as it may take these organisms 3-4 months to repopulate in high enough numbers to cause damage. Soil solarization can be considered another tool in your integrated pest management (IPM) toolbox, along with other cultural, physical, and chemical means of pest control.

Picture of raised bed garden covered in plastic.

A raised bed being solarized over the summer. Source: Evelyn Gonzalez, UF/IFAS Master Gardener Volunteer.

To properly execute soil solarization, the site should be in full sun and the existing vegetation removed, either by hand or with a tiller or other implement. Tilling can help loosen the soil surface and allow heat to penetrate deeper in the soil horizon. Before being covered with plastic, the area should receive rainfall or be irrigated, as the water will help conduct heat to greater depths. The next step is to cover the area with plastic. Note that this can also be done over raised beds! Clear plastic is best for maximum solar radiation penetration. Black plastic will heat up mostly on the surface and opaque plastic sheeting may not let enough light in to get temperatures high enough. The plastic should be slightly larger than the area covered, as the edges will need to be buried to create an air-tight seal. It’s recommended to leave the plastic in place for at least six to eight weeks, just in time to begin fall gardening preparations.

It’s important to monitor the site while it’s “cooking” to look for any holes that might appear. Small holes can be repaired with duct tape, while large holes or rips in the plastic may require starting over. Overlapping strips of plastic is not recommended since too much heat will be lost.

You may be wondering what happens to all of the good soil microbes. Well, unfortunately, they are also either killed or suppressed. Fortunately, researchers have found that they are able to repopulate quicker than the pest organisms, especially in soils with a good amount of organic matter.

Much more information on soil solarization can be found in these two documents:

Preparing Your Vegetable Garden

by Roy Carter | Sep 23, 2014

Healthful outdoor exercise, a feeling of accomplishment, and potential saving on the family food bill are good reasons why more and more Floridians are turning to home vegetable gardening.

Image Credit: FAMU

Usually, the most physically challenging part of a vegetable gardening project is to get the soil ready for planting. However, whatever you do, don’t give in to the temptation to cut corners on this phase of the operation. If you do a poor job of preparing the soil, you can expect poor results from your garden, even if you work hard on planting and cultivation. If you’re planning a large garden, you may want to rent a rototiller or even a small tractor and plow, to use in preparing the soil. But, for a small backyard garden, you can do the work with a spade or shovel.

The time to begin soil preparation depends to some extent on what’s growing on your garden site now. If you have heavy weeds, or a cover crop, you intend to turn under; you should start a month to six weeks before planting. This also is the time to add lime, if needed.

If you’ve kept the garden site fallow, or you plan to remove all vegetation and no lime is required, you could prepare the soil and plant within two or three days. However, if you plan to work extra organic matter into the soil before planting, you should start two or three weeks ahead of time.

To prepare the soil, dig down six to eight inches, and turn each shovelful completely over. If you’re turning in weeds, or a cover crop, you should remove all the woody plant material as it won’t decompose very well.

After the soil is turned, break clods and level with a rake. Do this as soon as you can, to prevent excess drying of the soil, and to keep good soil texture. This is important, because a finely pulverized soil surface will make planting easier, give you better seed germination and help insure a more even stand of vegetables. It’s especially important to have fine textured soil when planting small-seeded crops, like carrots.

In some soil, it’s also necessary to add some kind of liming material well before planting at the same time you turn the soil. Lime reduces soil acidity. Without going into a chemistry lesion, lime adds calcium to the soil and makes minor elements move available to plants. The most commonly used form of lime is dolomite. Besides calcium, dolomite provides magnesium another important plant nutrient. [important]You should add lime only when a soil test indicates the need for it. Too much can be as bad as too little. [/important]

If a soil test indicates your soil is too sweet, or alkaline, you may need a special fertilizer program. The best thing to do before liming or adding sulfur to reduce soil pH is consult your local County Extension Office.

To summarize briefly, to have a good garden, you need to prepare the soil properly. Be sure to start far enough ahead of planting to allow organic matter to decompose fairly well. Turn the soil to a depth of six or eight inches. Make sure you have a level, finely textured surface before planting. If a soil test indicates lime is needed to give your garden plot the right acid level, it should be applied when your turn the soil.

For more information on garden plot preparation:

Florida Vegetable Gardening Guide

Soil Preparation and Liming for Vegetable Gardens