Organic matter is an inherent property of the soil that is the result of the growth and decay of plant roots. Little organic matter is returned to the soil from plant parts which grow on the surface. At least 30 percent of the root system is replace each year, thereby supplying the organic matter in the soil. Less than 10 percent comes from the breakdown of material grown on the surface. Heavy accumulations of surface material result in decreased plant growth, decreased root growth and, consequently, decreased soil organic matter.
Soil erosion increases as the length of time between burning and spring green-up is increased.
When wildfire occurs in the late summer, fall or winter, the soil is exposed to the pounding of randrops and soil compaction and erosion may be significant. Raindrop impact causes puddling and soil crusting resulting in decreased water infiltration and increased surface runoff. This causes erosion. Fifty-five years of research on burning grasslands at Kansas state University has shown that timing the burn as late in the spring as possible, just after the WSG breaks dormancy but before they exceed 3 inches in new growth, will minimize puddling and crusting and will soon provide a protective layer of grass leaves to intercept raindrops. Burning will also result in increased microbiological activity and root development which breaks down soil minerals to form new soil and release nutrients.