What Is Aerial Mulching?

Protecting the Watershed

• After large areas of forest are destroyed due to fires or flood, the soil will wash into streams, rivers and nearby lakes. When this occurs, it often severely affects wild aquatic creatures and commercial fisheries. Hand mulching with straw has proven to help prevent this type of erosion, but it is a “long and expensive process,” according to the U.S. Forest Service, and is nearly impossible in steep, inaccessible areas. Aerial mulching is the method of choice because the mulch reduces the impact of rain; keeps soil, seeds and soil nutrients in place; and reduces surface runoff.

Responsible Agencies

• The United States Department of Agriculture, the U.S. Forest Service, and local agencies and businesses participate and cooperate in aerial mulching. In the so-called Trough fire that occurred in the Mendocino National Forest in California in 2001, the California Straw Supply Co-op participated along with governmental agencies by supplying bales of straw that helicopters dropped. Many people become involved in a large aerial mulching effort, including planning and work crews, truck drivers, and helicopter pilots.

Type of Aircraft Used

• Helicopters are the primary type of aircraft utilized during aerial mulching projects. This type of aircraft works well because it is able to maneuver into steep ravines and other inaccessible areas and to hover low to the ground, ensuring that the straw bales land where they will be most effective.

Cost of Aerial Mulching

• In the 2001 Trough fire, the estimated cost per acre was $450 for a 60-acre test area. In a 2002 test conducted in the same burned area, the cost of dropping a newly formulated hydromulch was $3,000 per acre. This test’s goal was to conserve as many native plants as possible by eliminating the burial that occurs during standard aerial mulching. Follow up studies showed that the experimental mulch was intact after 6 inches of rain and that native plants had begun to germinate through the mulch. It also prevented surface erosion and some stream erosion.