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PHYTOEXTRACTION Barley roots can absorb toxins in the soil and distribute it throughout the plant.

Toxic soil

Find the right plants to clean your soil

By KATE RUSSELL

Growing leafy greens and other edibles in toxic soil can make you sick. In some cases, it can kill you. Often found under landfills, junkyards and factories, toxic soil is increasingly found in urban areas. Unfortunately, fill dirt used when building homes in years past may have been brought in from questionable locations. Without a soil test, you don’t know what is in your soil.

Healthy soil contains a balance of organic matter, air, water and minerals used by plants as food. Some of those helpful minerals, such as boron or molybdenum, can reach toxic levels. So can organic pollutants, including creosote, fertilizers, herbicides, industrial solvents, pesticides and petroleum products. You may even have radioactive materials in your soil.

Soil toxins leach into groundwater. They can become part of the dust that you inhale and the foods you eat. These toxins can be absorbed through your skin and may coat produce you grow or buy. To be safe, leafy greens and root vegetables should be rinsed before using.

The only way of knowing whether or not you have toxic soil is with a lab-based soil test. They are inexpensive and extremely valuable, especially if your soil is toxic. Contact local Master Gardeners or look online for soil test labs.

If a soil test indicates the presence of toxins, you have options. Traditionally, toxic soil was dug up and buried somewhere else. Today, researchers are looking to plants for a solution. As plants absorb water and nutrients, they also take up some of these toxins. This is called phytoremediation.

Soil toxins may be absorbed by roots and distributed throughout the plant (phytoextraction) or released into the atmosphere through transpiration (phytovolatilization). Root secretions can stabilize some soil toxins (phytostabilization) while other root secretions can break down organic toxins (phytodegradation) and others stimulate soil fungi to break down organic fungi (phytostimulation).

Only specific varieties of certain plants are good at dealing with toxic soil. For example, willow is considered to be very good at removing and neutralizing toxins, but not all willow species. Studies have shown that “Salix matsudana” and “S. x reichardtii” are far more effective than other species.

Barley, beets, hydrangea and sorghum are excellent phytoextractors. Many trees can accumulate radioactive particles. Just remember that plants used in phytoextraction should be removed from the site and disposed of safely. Contact your local waste authorities for more information.

Using plants to clean toxins from soil may take longer, but it’s inexpensive, environmentally safe, and it preserves topsoil. Did you know that some companies extract these toxic and sometimes valuable minerals from plants? This is called phytomining.

Get your soil tested and find out which plants can help you clean your soil.