Use of Wood Ash as Soil Amendment on Annual Rangelands

Use of Wood Ash as Soil Amendment on Annual Rangelands

Summary

Activity to-date includes meeting with participating ranchers, selecting study sites, building 25 exclosure cages, conducting baseline soil sampling, spreading ash on plots and photo recording. Most of this work was done in September, October and November, 2011. Early rains were followed by nearly two months of drought, which has delayed ash incorporation and grass response.

Objectives/Performance Targets

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

*Analyze soil and vegetation differences between ash treated and untreated areas.

*Determine forage production changes.

*Record changes in plant diversity and density.

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

*Determine if grazing season has lengthened.

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

*Provide outreach to cogeneration plant owners on ash usage, application requirements, time of use and other issues specific to rangeland application.

*Determine carbon baseline data and determine sequestration potential for ash-treated annual rangeland.

*Publish findings and post on website.

Accomplishments/Milestones

1. Fly ash was spread at two application rates on five ranch sites within Butte County (Northern California) in November 2011. No tillage was involved. Ash was spread into standing RDM using natural rainfall to filter ash into soil structure. The study includes notation of ash migration from water and wind affects, as well as soil and vegetation changes.

2. Lack of consistent rainfall during the 2011-12 wet season resulted in inconsistent grass growth, infiltration and general data quality. The study is being extended through the 2012-13 rain season in hopes of better conditions with more comparative data.

3. Initial soil baseline data was collected for each site.

4. We have built exclusion cages that protect sample areas from grazing, since grazing is a component of the larger ash application areas. We want to observe how ash affects animal grazing behavior, based on assumed changes in forage quality from NPK and other mineral amendments.

5. We have contracted with Covanta Energy to have 40 tons of fly ash delivered to a central location from which we loaded into a spin spreaders used in commercial fertilizer applications and traveled to each study location. Application rates were monitored using five catch pans placed across the spread bandwidth. Several repeats were necessary to reach the target rates of 7.5 and 15 oz/square foot, which equaled approximately 10 and 20 tons/acre.

6. During the rain months, visual observation noted any surface movement of ash from runoff and grazing behavior. From earlier tests using sheep, expectations were that ash immediately improved forage quality and intensive grazing. The sheep ranch used rotational grazing, which protected the test plots very well. The cattle operations practiced set stocking for most of the green period, which resulted in over-impacting the larger test areas and some exclusion cage disturbance.

7. Our remaining work includes visual observation and maintenance, building protective electric fencing, soil and vegetation collection and testing and field day events to show results.

8. We have been invited to present a slide lecture for the California Climate and Agriculture Network Symposium in February to demonstrate fly ash soil amending as an effort to build resilience to the threat of climate change.

Impacts and Contributions/Outcomes

Based on prior testing, fly ash has the ability to markedly improve annual rangeland forage quality and quantity, extend grazing season, shift species to legumes, deepen root systems, improve wildlife habitat and generally improve rangeland production levels. Prior tests showed an average of 2.1 tons/acre increased forage over control plots in four areas of our ranch. The high rates of potassium, phosphorous and some nitrogen favored annual legume growth, which in certain areas nearly overpowered grass varieties, thus vastly improving quality as well. The mix of forages retained its relative quality values throughout summer months as dry feed. This led to 60 days of extended grazing for lamb growth and nearly complete forage needs for ewes post-weaning until fall rains began the next cycle.

This study also will determine if ash can be applied in standing RDM without risk of movement by water runoff or wind. If so, use of ash on suitable rangeland will be the best means of soil amendment and forage improvement across a wide landscape. Current regulations stipulate that ash be tilled-in, which has limited its use to farmed acreage.

Another study component will include exploring a suitable business model that will address environmental liability, accountability, application costs and other contingencies.

A final outcome will be to bolster local co-generation sustainability by reducing ash removal expense. Local forest and agriculture industries rely on the facility to provide moderate revenue from wood chips and orchard removal to support those activities.

• Fly Ash Analysis

Collaborators: