Potato production is a dominant sector of agriculture in northwestern Washington. In Skagit County potatoes are grown on 12,000 acres and the average yield is 20-25 tons/acre. Since potatoes have a high impact on soil nutrition and organic matter, soil quality has become an important priority for potatoes farmers in this area. Arable land is limited in northwestern Washington and land sharing is a common practice in Skagit County. However, it is often difficult for potato farmers to find viable rotation crops based on the extensive amount of acreage they occupy.
Harmony Fields, LLC is an expanding sheep creamery and organic herb farm based in Bow, WA. Fifty percent of this operation’s land is rented from a neighboring potato farm. Harmony Fields is interested in increasing pasture access for their animals over time and require more land each year. It had been well documented that livestock rotations in crop production systems can have positive effects on the soil across farm scale and production type. Also, compost and manure additions can have varying effects on potato quality and disease. More information is needed to better understand the impact of small ruminant grazing rotations in potato production systems.
This project would investigate the consequence of integrating sheep grazing in a potato rotation system by investigating how pasture and sheep manure inputs affect soil-borne tuber disease incidence and severity and soil organic matter quality and nutrition. The project would also document how larger, more established farms can engage with smaller, first generation farms in a relationship that is mutually beneficial.
- Investigate the influence of sheep grazing on potato and soil quality.
- Determine optimal pasture species diversity and access for dairy sheep health in northwestern WA.
- Distribute information to regional and national producers.
Potato health and soil quality
In 2019, potato plots were established at Harmony Fields. Plots were established in an area that has been grazed by dairy sheep for the past 8 years (2011-present). Potato plots were established (3 varieties (representative red, yellow and fingerling potatoes), 3 reps) in May 2019 and managed following organic potato management strategies as per potato growers protocol. In-row plots were 10-ft long and set up in a randomized complete block design. This trial will be repeated in another area of the same field in 2020 using the same varieties.
In fall (October 2020) potatoes were harvested and examined for size, yield (lbs) and soil borne disease incidence and severity. Soil quality parameters (Cornell Soil Health Lab assessment protocol) was recorded before planting both years. These include available water capacity, soil proteins, active carbon, organic matter, pH, extractable potassium, extractable phosphorous, minor elements, soil respiration, and aggregate stability.
Samples of potatoes (‘Chieftans’-3 plants per section) from Wallace Farm commercial potato field were sampled in September 2019 and inspected for disease and size. Samples were taken from an area previously grazed by sheep (2 years) and not grazed (corn, barley rotations).
Field trial was planted May 28th 2019 and harvest October 10th 2019. Varieties planting: Chieftan, Yukon Gold, Banana Fingerling
Greenhouse microplot experiments
Supplemental greenhouse studies, using soil from sheep pastures from Wallace Farms and relevant potato varieties (see above) were set-up in May 2020. Potatoes were grown in modified buckets (5 gallon) using the collected field soil. Moisture was kept at field capacity using a micro-sprinkler system. Potatoes were assessed at the end of the season (Oct 2019) for disease incidence and severity and size/yield as mentioned above. The experiment was set up as a randomized complete block design (3 treatments, 3 reps) at Harmony Fields. This will be repeated in 2020.
GH trial was planted June 27th 2019 and harvest October 30th 2019. Varieties planting: Chieftan, Yukon Gold, Banana Fingerling
Pasture mix plots
Five varietal mixes of grass and legume pasture species were tested in small plots (4’ x 4’) at Harmony Fields. They were planted in spring/fall (2019) and will be repeated in spring (2020). The experiment was set up in a randomized complete block design (3 reps, 5 treatments). Pasture establishment was verified by identification of surviving pasture plant species at 6 and 12-months post-planting. Percentage of coverage establishment as well as plant samples were collected in October 2019 sent to a regional lab for nutritional analysis. Future samples will be collected and sent to the same lab.
Spring Pasture Trial plated May 28, 2019. Fall Pasture Trial Planted October 9th, 2019.
These studies help to discern if/how sheep grazing impacts potato and soil quality. Additionally, ideal pasture mixes and pasture planting recommendations will be determined for dairy sheep in northwestern Washington.
Results (Progress Report March 15, 2020)
Farmer/Dr. Gigot has been in consultation Dr.Kerr via email and had specific project meeting in August 2019 (Harmony Fields) and December 2019 (WSU). Soil sample analysis is needed spring and fall 2020 as well as 2019 pasture species planting (spring planted-12-month and fall-planted 6 month & 12-month) analysis. The 2020 potato and spring pasture plantings will take place as planned. All data will be analyzed in conjunction with the technical advisor in summer/fall 2020.
Image 3. Pre-flowering greenhouse trial potato plants
Image 10. Spring-planted pasture variety trail at 6 months
Table 1. 2019 In-Field Plots
Table 2. 2019 Soil Health Tests
|HF Fields||Wallace Field 1||Wallace Field 2|
|ACE Soil Protein||21.2||19.3||16.9|
Table 3. 2019 Greenhouse Field Trial
|REP||TYPE||Weight (oz)||ROT||Silver scurf||Rhizoctonia|
Table 4. 2019 Pasture Field Trial
Table 5. 2019 Pasture Trial Analysis
|Neutral Detergent Fiber||55.74||56.53||60.51||37.87||24.87|
|Acid Detergent Fiber||27.84||22.69||32.26||23.75||21.74|
Table 6. 2019 Existing Pasture
|Acid Detergent Fiber||4.42||4.31|
|Total Dig Nutrients||10.86||11.54|
|Crude Protein %||19.72||12.89|
Samples from Wallace field showed a low incidence and severity of Rhizoctonia and Silver Scurf (data not shown/Image 13). No scab was detected. In a Year 1-checkin interview with the field manager/co-owner, they did not report any tuber abnormalities or yield issues from the sampled field with a history of sheep grazing.
Educational & Outreach Activities
Four project-related blog posts are planned for 2020 on the HF website. Talks about results are scheduled for fall 2020 (Tilth Alliance conference, Dairy Sheep Association of NA, and Washington State Sheep Producers). A farm-walk presentation is being planned for local veg/potato farmers (Sept) and well as a potential talk at the WSU Field Day (July 2020) and Western Washington Potato Meeting (Feb 2021). Farmer/Dr. Gigot also participated in a SARE podcast interview (Nov 2019) that should air in 2020, but that date needs to be confirmed.
Data will be compiled into a short extension publication for dairy sheep farmers and/or potato farmers interested in diversifying rotations. An article describing the participants, findings, and exploration of land sharing will be submitted to Agriculture, Ecosystems, and the Environment. Relevant newsletter/articles (WSU Green Times, Capital Press, DSANA) will also be pursued to document and share the findings.
- First blog post 6/25/20: https://harmonyfields.com/farm-journal/sheepandsoilhealth/
- On-Farm workshop will be scheduled by May 2020.
Regular SARE reports will be submitted on the project as required.