Home gardeners know all about patience and tender-loving care required to develop a green thumb. We want to do all we can to set our plants up for success and give them the best chance of survival and prosperity. This begins with your growing medium: soil!
Healthy soil free from weeds and disease is the key to producing healthy plants. While there is some debate on the necessity of soil sterilization for plant prosperity, several benefits are depending on the type of gardening you do.
If your plants are prone to disease, or your garden looks more like a bed of weeds, soil sterilization may be your solution!
What is Soil Sterilization?
Soil sterilization is a means of killing harmful organisms, pathogens, and weed seeds found within the soil. This is done by either treating the soil with chemicals or raising and holding the temperature of the soil for a certain amount of time.
Why Would You Want to Sterilize Soil?
When dealing solely with mature plants, soil sterilization isn’t necessary. This is because mature plants are much better at coping with the soil deficiencies found in recycled or poor soil.
However, soil sterilization is a great first step when you plan to re-use your garden or potting soil. It is also helpful when germinating seeds, propagating cuttings, or transplanting seedlings, juvenile or vulnerable plants. In these cases, the deficiencies found within old soil hinder plant development and may cause premature plant death.
If you’re concerned about the spread of weeds, fungal spores, or disease throughout your garden, soil sterilization is a great fix. This covers your bases and prevents the loss of an entire crop or plant grouping.
Additionally, using sterile soil as a starting point prevents future weed, pest, or disease problems from popping up. Thus saving you money on potentially harmful herbicides and pesticides.
Methods of Soil Sterilization
There are two main methods of soil sterilization: chemical and heat treatments. Use either method to spruce up old soil and take control of your growing environment.
Regardless of the sterilization method, the first step is to prep your soil by breaking up existing clumps and removing any previous plant/root debris.
Chemical treatments are usually used in large-scale commercial operations. While at-home applications are fairly easy to use, there are some hazards associated with using chemicals in your garden. Follow the manufacturer’s instructions carefully to minimize the health risks posed to the applicator as well as those near the application site.
The purpose of chemical treatments is to infuse the soil with gases that eradicate certain pests and pathogens within. The issue is that certain chemicals target specific organisms in the soil and do not eradicate all of the issues. These chemicals are also responsible for killing beneficial organisms along with the bad. Replenish healthy microbes after sterilization by adding nutrient-rich material like composted tea!
The two most commonly used chemicals in at-home soil sterilization are:
1. Hydrogen Peroxide
Hydrogen peroxide can be found at any drug store and makes a great sterilization agent. A solution of hydrogen peroxide and water may be sprayed into the soil for sterilization purposes.
Formalin is a mixture of formaldehyde and water which may be sprayed into the soil for sterilization.
Apply your chemical of choice properly and adhere to the quarantine period after sterilization. This period is necessary for the chemicals to degrade and be flushed out of your soil; preventing lingering residue that may be taken in by plants.
It is important to note that using a chemical sterilization method is not recommended for greenhouses. Chemical fumes trapped in these enclosed spaces have the potential to cause harm to your other plants.
Due to hazards that arise from chemical use, heat sterilization treatments are recommended for home gardening.
Use one of four heat sources to sterilize your soil, raising its temperature using steam or direct, dry heat. Adhere to appropriate temperature specifications and duration of heat exposure to avoid releasing toxins from scorched organic matter.
While some may argue that heating your soil does not make it completely sterile, this provides the benefit of not killing off as many beneficial organisms and bacteria that thrive in healthy soil. Heat exposure also helps speed up the decomposition of organic matter within your soil; releasing magnesium, potassium, nitrogen, and other nutrients that plants need for proper growth.
There are three heat sources to use at home to sterilize small to medium batches of soil:
1. Pressure Cooker or Steamer
If you’re looking for a cheap and efficient way to eradicate soil pathogens, these in-home heating methods work wonders!
What about large quantities of soil? If you can’t physically bring all the soil you would like sterilized into your home, the fourth heat source to utilize is the sun!
Solarization uses thin, transparent plastic to trap sun rays and heat the moist soil beneath. Solarization is a great method for sterilizing large batches of soil using natural energy from the sun.
Depending on the climate, solarization may take anywhere from 4 to 10 weeks to properly sterilize your soil. It is well worth the wait for a large area of weed-free, solarized soil!
While the heat from the sun eradicates both harmful and beneficial organisms, solarized soil is repopulated rapidly by beneficial microbes. This rapid re-colonization corrects the initial loss of important bacteria cultures within the soil. Likewise, earthworms with burrowed into the cool ground beneath solarized soil can move into your treated soil after sterilization.
To Sum it up
Soil sterilization is a great tool to set your plants up for success and gain control of your growing environment. It is most important when re-using old soil that may contain weeds or harmful pathogens. Sterile soil is also recommended for germinating seeds, propagating cuttings, planting seedlings, and transplanting juvenile or vulnerable plants.
Use chemical or heat treatments to eradicate harmful pathogens, weeds, and other pests from your soil and ensure plant prosperity and garden health. Sterilize small or large batches of soil using common household heat appliances or the natural power of the sun!
Providing your plants with a healthy growing medium is key for preventing disease and weed build-up in your backyard garden space!