Use of Wood Ash as Soil Amendment on Annual Rangelands

Project Overview

Project Type: Farmer/Rancher
Funds awarded in 2011: $28,995.00
Projected End Date: 12/31/2013
Region: Western
State: California
Principal Investigator:
Mel Thompson
Sierra Farms
Glenn Nader
University of California Cooperative Extension

Annual Reports


  • Additional Plants: native plants
  • Animals: bovine, sheep


  • Animal Production: grazing management, pasture fertility, range improvement, grazing - rotational
  • Crop Production: organic fertilizers, tissue analysis
  • Education and Training: demonstration, extension, farmer to farmer, mentoring, networking, on-farm/ranch research, participatory research, workshop
  • Energy: energy use
  • Farm Business Management: budgets/cost and returns, marketing management, value added
  • Natural Resources/Environment: carbon sequestration, biodiversity, habitat enhancement
  • Production Systems: agroecosystems
  • Soil Management: organic matter, soil analysis, nutrient mineralization, soil chemistry, soil quality/health
  • Sustainable Communities: new business opportunities, employment opportunities, sustainability measures


    This project attempted to quantify benefits from the use of wood ash on rangeland. Five locations were chosen, representing soil diversity typical of Butte County. Plots were 50’x100’, with ash spread at two rates, 10 and 20 tons/acre, on opposite strips within the plot. Four exclusion cages were used on the treated areas; two per application rate and one in non-treated adjacent area as a control sample.

    Sporadic, insufficient rainfall during the 2012 season prevented ash from filtering into the soil profile and produced so little forage that valid measurement was difficult. The project was extended one year, which resulted in slightly better conditions. Sampling occurred in May and June 2013 and is included in this report.

    Generally, response to potassium was greatest, showing in positive legume growth, with moderate nitrogen and phosphorous response. Rainfall amounts and timing varied across the five locations and seem to be the most significant variables in test results. Ideally this study should proceed for several more years in order to get a better assessment over average rainfall amounts.


    Based on prior, non-technical trials, the use of wood ash was seen as having noticeable positive results in production of legumes found in local annual rangelands. Species shifting toward increased legume content is a positive trend in rangeland livestock husbandry, wherever possible.

    Fly ash is a by-product of co-generation facilities that use ag and forest wood waste to turn steam-powered electrical generators. Recent interest in forest management and orchard replacement, combined with incentivized alternative energy production, has increased the potential for ash production. Prior ash waste from the local plant was being trucked approximately 100 miles to a landfill. Local ash usage on rangeland was seen as beneficial to both the co-gen facility and local farmers and rangeland owners. Approximately 16,000 tons per year would treat 800-1600 acres annually.

    The local plant employees 35 persons and contributes approximately $50 million yearly to the local economy in wages and associated business activity. Ash waste removal was a $1 million or more expense to the facility, while being a lost opportunity as a soil amendment. This study attempted to merge the two circumstances to the benefit of each.

    Rangeland soils in Butte County tend to be slightly acidic, red clay loam with surface rocks and underlying hard pan or lava cap. These conditions have discouraged attempts at cultivation even on relatively level terrain. Vegetation is mostly annual grasses and forbs, with major invasions of medusahead and yellow starthistle. Plant diversity is fair and plant density (soil coverage) often is very low. Initial trials with wood ash have shown dramatic improvement in forage growth without seeding, especially in annual legumes. The native annual legume seedbank is present, while ash, with high potassium and moderate phosphorous, sulphur and nitrogen levels seems to be the catalyst. High calcium levels tend to loosen the clay structure, allowing improved soil porosity, water infiltration and reduced runoff.

    Project objectives:

    The objectives of the project were:

    1. Determine best means and rate of ash application, considering area coverage, labor requirements, vegetation response and impact on RDM.

    2. Analyze soil and vegetation differences between ash-treated and untreated areas.

    3. Determine forage production changes.

    4. Record changes in plant diversity and density.

    5. Observe changes to soil texture, porosity and infiltration rates.

    6. Determine if grazing season has lengthened.

    7. Provide outreach to other ranchers and interest groups as to findings, benefits and unforeseen problems.

    8. Provide outreach to co-generation plant owners on ash usage, application requirements, time of use and other issues specific to rangeland application.

    9. Determine if carbon sequestration is enhanced by ash usage on annual rangelands.

    10. Publish findings and post on website.

    The overriding objective is to expand on observed vegetation changes found in earlier experiments and make ash application acceptable to a wider group of ranchers, while simultaneously anchoring the local biomass conversion facility by demonstrating safe, feasible means of utilizing its ash by-product.

    A long-range objective is to form an LLC of rangeland owners to contract ash dispersal from the facility, with the ability to absorb full application accountability for the product's safe usage. Biomass conversion plants commonly pay for ash removal, which, if possible, could add more incentive toward improving range conditions, as well as serve as a model for similar applications in other areas.

    Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.