Wildfires fueled by drought, high winds and mild temperatures have led to the demise of thousands of acres of pastureland in Oklahoma and Texas. What impacts will these unplanned fires have on the soil?

Though fires charred large areas of land, many areas experienced a less intense fire due to high winds pushing the flames rapidly across pastureland. In these areas, it is unlikely that the soil surface was heated enough to negatively affect weed seed germination. Also, exposed blackened surfaces will absorb more sunlight and warm up earlier than usual. As a result, weed infestations may come earlier this spring. That means weed control and fertilization will be essential this spring on introduced pasture (i.e., bermudagrass). As with weed seed germination, the soil was not heated enough to “kill out” bermudagrass pasture. Bermudagrass is a vigorous species and has many growing points both above and just below the soil surface. The return of a “normal” weather pattern this spring, along with a good fertilizer program, will assist in bringing these pastures back to life. The key to success with weed control is to properly identify weeds in order to select the correct herbicide for the job.

With the lack of vegetation, it is likely that soil erosion will be a problem with the arrival of spring rains. Root materials will continue to hold the soil together in most areas. However, sheet erosion from the soil surface will be a concern in the early spring. Do all you can to rejuvenate vegetation as quickly as possible to lower the risk of losing large amounts of soil by erosion.

Soil fertility will be impacted, but only for a short while. The standing plant materials and thatch lying on the soil surface comprises a fair amount of nutrients. Fire will chemically change these organic plant materials, mineralizing both nitrogen and phosphorus and making them quickly plant available. Note that the amount of mineralized nutrients will be minimal and not enough to support forage production through the entire growing season. With the return of spring, these available nutrients will be used by either desirable plants or weeds. Again, this stresses the importance of good weed management this spring.

Jeff Ball
Soil and Crops Specialist