What Is Burnt Soil?

Feel the Burn

• Controlled burns are usually conducted in order to rejuvenate land by adding nutrients, removing competing vegetation and revitalizing the soil. When crop plants in a field carry diseases, burning their stubble can be an effective way to reduce the remaining pathogens. Sometimes controlled burning is prescribed for forest land to change its composition, fostering the growth of plants different from those in a more established forest. It also may be used to improve access. All controlled burns should be conducted with professional help.

Consider the Benefits

• Setting fire to a patch of land has several benefits for the soil. It increases nitrogen levels in the soil by incorporating ash from plant refuse. It also gets rid of that refuse, reducing the need to clear plants' remains. It kills weeds and many kinds of weed seeds. The fire's hot temperature also kills insects, their eggs and larva, depending on their life cycle stage. Some grasses and other plants are revitalized by a burn and use the resulting extra nutrients to grow lusher and fuller the following year.

Understand the Detriments

• Unfortunately, controlled burning is widely regarded to have more detriments than benefits. Because fire is indiscriminate, it kills various kinds of plants, including those that may contribute nitrogen-fixing properties or other nutrients to soil. Old plant roots that fix water in soil also are burned, possibly reducing the land’s ability to conserve moisture. Oftentimes, the fire's heat radiates to about only a 1-inch depth in the soil, missing some weed seeds and insects that overwinter deeper in the soil.

Don't Try This at Home

• Soil burning is a farming or forest practice, for the most part, and isn’t nearly as manageable on small properties such as backyard gardens. Although burning a garden may have some weed-killing and soil-improving effects, don't attempt to burn more than a small pile of plant refuse. Because home yards may contain soil contaminants, such as toxic substances spilled by previous owners, controlled burning in those locations can be much more hazardous than helpful.