Many pasturelands in western Washington are not actively managed or renovated after
the initial pasture seeding. Compaction, depletion of soil nutrients, and domination by
aggressive and unpalatable grass species lead to poor forage quality and reduced forage
quantity. Livestock producers recognize the need to improve pastures, but lack specific
information necessary to evaluate the risk and benefits of different pasture renovation
techniques. Conventional tillage and re-seeding is a lengthy, costly process that disrupts
soil structure and function and may favor invasive weeds, increase soil erosion, and
exacerbate loss of organic matter. A few producers practice annual aeration as a
management technique to oxygenate the soil, increase water infiltration, and improve a
seed bed. Research results on the effects of aeration vary widely. Variation in soil types,
climates, and vegetation also makes extrapolating data problematic. This leaves
producers with little data to assess the long-term impact on soil health or forage quality
and quantity, so the expense and risk of implementing this technique remain a barrier to
adoption. Sheep ranchers Adam Greene and Sarah Pope will perform field trials,
collecting data and demonstrating practices. Trials will focus on aerator use versus no use
(control) and compare over-seeding with and without aeration to unseeded areas.
Research design, data collection and analysis, and outreach support will be provided by
Dr. Brook Brouwer and Angie Freeman Shephard, MS of Washington State University
Extension San Juan County. This study will increase awareness of pasture renovation and
management best practices with a well-placed demonstration to other farmers/ranchers.
Information and results will be shared widely through field days, fact sheets, articles, and
on the extension website.
1. Measure how aeration and over-seeding impacts soil health for three years (Years 1-3)
2. Measure how aeration and over-seeding impacts forage quality/quantity (Years 1-3)
3. Measure establishment of over-seeded legumes in aerated vs. non-aerated (Years 1-3)
4. Quantify economics of aeration and over-seeding: cost to implement and estimated
value of benefits or negative impacts (Years 2-3, results published in Year 3)
5. Encourage pasture renovation by illuminating risks and benefits (Years 2 and 3)
6. Quantify adoption impacts using before-and-after questionnaires (Years 1-3)
Oak Knoll Pasture Trial Methods
- Collect ~10 cores per plot to 12 in depth
- Mix in 5 gallon bucket
- Split sample in half, 1 for Haney test and 1 for agronomic soil test
- Push penetratrometer into soil until 300 PSI using 1/2 cone tip
- Record depth (inches) at which 300 PSI is reached
- Repeat measurement 10x per plot
Percentage Ground Cover
- Estimate % Bare Ground, % Litter, % Grass, % Legume, % Other forb, % Birdsfoot trefoil
- Total may exceed 100%
- Record values for 4 randomly placed quadrates per plot
- If time allows, record species present—not critical
- Cut vegetation to ground level
- Place 6in ring 3in into ground
- Press soil against inside edge of ring
- Lay plastic sheet
- Pour 444ml of water into ring
- Remove plastic and record time until water has infiltrated (Time 1)
- Repeat (Time 2)
Educational & Outreach Activities
An educational and outreach event occurred in 2018 and one is occurring Feb 2nd, 2019.
- Outreach: A farmer who owns and operates a local farm (all-year market garden and meat animals) was curious about the program and aeration. She ended up borrowing the aerator and ran it in a more aggressive mode (blades out at 10 degrees and running over the same field at least 3 times at 7-9 mph). She was very happy with how the alfalfa grew in that field that year and would like to try it again next year.
- Tour: 9 individuals from the conservation district and Washington State Dept. of Ecology visited the farm to look at a separate project supporting no-till seeding practices in the county, which the farm is participating in. They received an overview of the aeration project and toured the pasture.
- Workshop: the 2019-Ag-Summit-Schedule_2019_01_08 is occurring Feb 2nd and 3rd, 2019, and a half day session on “Pasture and Hayland Evaluation” will be hosted at the farm, where this research project will be highlighted and discussed. The speakers are Marty Chaney, USDA-NRCS Agronomist, and Brook Brouwer, WSU Extension and project coordinator.