Using Biochar to Improve Soil Quality on Decommissioned Roads
U.S. National Forests have over 380,000 miles of roads. Many of these roads are over 25 years old, sub-standard, compacted, and invaded with non-native plant species. Roads that are decommissioned need to be restored so that they recover their hydrologic function, soil productivity, and native vegetation.
Restoration treatments involve adding agricultural or wood straw, which are successful to varying degrees. Forest Service scientists tested the use of biochar as a restoration medium, created by using fast-pyrolysis and beetle-killed lodgepole pine, to evaluate changes in soil bulk density, moisture holding capacity, and re-vegetation. Biochar is created from excess woody biomass that would normally be burned. Biochar use on forest sites can (1) sequester carbon, (2) improve soil moisture conditions, (3) decrease soil bulk density, and (4) improve native vegetation success. These four attributes combine to improve the success of soil restoration activities, particularly on drought prone sites. The scientists used bulk biochar at three rates: low (1 ton/acre), medium (5 tons/acre), and high (10 tons/acre). They also looked at biochar pellets (1 ton/acre), wood straw (applied to 40-60 percent cover), and a “no amendment” treatment. They sampled the adjacent undisturbed forest and used this as a benchmark for soil recovery on the road prism. After two years, the high biochar plots had 28 percent lower bulk density in the surface four inches than the original road surface. In addition, the high biochar plots had a moisture content of 25 percent, whereas the undisturbed forest was 21 percent. Native forbs are replacing the non-native grasses on most amended plots, but there was no clear difference among the amendment types. Understanding application rates and soil responses in many different temperature and moisture regimes is critical for restoring site quality.
Forest Service Partners