Increasing adoption of reduced tillage strategies on organic vegetable farms in the maritime

View the project final report

• 2015 annual report
• 2016 annual report

Commodities

• Vegetables: beans, broccoli, cucurbits

Practices

• Crop Production: conservation tillage
• Education and Training: demonstration, extension, farmer to farmer, on-farm/ranch research, participatory research
• Energy: energy use
• Farm Business Management: budgets/cost and returns
• Natural Resources/Environment: carbon sequestration, indicators
• Pest Management: mulches - killed, cultivation, mulching - vegetative
• Production Systems: agroecosystems, organic agriculture
• Soil Management: earthworms, organic matter, soil analysis, nutrient mineralization, soil microbiology, soil chemistry, soil physics, soil quality/health

Grower interest in reduced tillage techniques stems from concern over soil quality and energy use. Tillage decimates large-bodied soil organisms, reduces soil carbon storage and weakens the stability of aggregates. Yet, organic vegetable growers in the Pacific Northwest currently pass over their fields 10 to 20 times annually to incorporate cover crops and amendments, prepare the soil for planting, and manage weeds. In response to the interest in tillage reduction, our syndicate of growers, researchers, and Extension educators has worked collaboratively to develop and test reduced tillage strategies for organic vegetable production in the Pacific Northwest since 2009. Incorporating reduced tillage into organic vegetable cropping systems requires careful integration of cover crops with equipment. Cover crops for reduced tillage systems must be winter hardy, produce sufficient biomass to smother weeds, mature early, and preferably add nitrogen to the system. Tools must effectively kill the cover crop without tillage and also prepare the soil to receive a transplant or seed. 

Our goal is to increase organic farmer economic and environmental sustainability through soil conservation and reduced tillage. Through a previous SARE Project (SW11-072) we carried out four on-farm experiments, cover crop variety trials, and initiated a long-term systems experiment. This current project (SW14-013) continues our systems-based work to develop and implement reduced tillage strategies for organic vegetable cropping in the maritime Northwest and other northern climates. Our future focus is to reduce risk for early adopters of reduced tillage by sharing successes and failures. We will also encourage more wide-spread adoption of reduced tillage by building on our previous experience to address specific obstacles and remaining questions, including:

• Which implements and strategies are most effective to manage residue in zone-tilled ground? (Objective 1)
• How does reduced tillage affect nutrient cycling and fertility management? (Objective 2)
• Which cover crops, mixes, and termination strategies perform best? (Objective 3)
• What specific challenges and opportunities do continuous reduced-tillage present? (Objective 4)

We will address these questions and extend our outreach (Objective 5) by:

1. Facilitating research with seven commercial organic vegetable producers. We will improve residue management and compare cover crop termination strategies through on-farm trials and demonstrations. (Objectives 1, 3, and 5)
2. Continuing an on-station long-term reduced tillage cropping systems experiment with three cash crops in rotation and adaptive management to include new cover crops and equipment improvements. Specifically, we will implement more aggressive zone tillage. (Objectives 1, 2, and 4)
3. Executing 6 cover crop variety trials at two different research stations. (Objective 3)
4. Reaching out to producers through field days, farm walks, articles, a video, and presentations to state-wide, regional, and national audiences. (Objective 5)

• Develop and analyze best strategies for cover crop residue management in zone tilled organic agriculture systems: Zone tillage has thus far provided the most interest among cooperating growers. Our current zone till treatment will be modified to provide more aggressive in-row tillage and a second zone tiller will extend our ability to reach more farms. We will measure the success of zone tillage by comparing soil temperature and crop yield in zone-tilled and full-tilled treatments in on-farm trials and in our long-term reduced tillage systems trial. We will also measure zone tillage success by comparing the density of volunteer cover crops and weed management in the inter-row for the two cover crop termination methods.
• Evaluate nitrogen cycling dynamics in reduced tillage organic systems:  Through our previous cover crop trials we have been able to identify a successful legume cover crop (Purple Bounty vetch) for inclusion in our long-term reduced tillage trial. We will focus our evaluation of nutrient cycling dynamics in tilled and reduced tillage treatments following vetch by measuring cover crop N at termination, cover crop decomposition rate dynamics, soil nitrate and plant uptake by broccoli through the season each year.
• Select cover crops and termination strategies for reduced tillage organic agriculture: Successful cover cropping is essential to reducing risk in adopting reduced tillage organic vegetable production. The cover crop must produce enough biomass to effectively suppress weeds and also reach a late developmental stage to mechanically terminate while accommodating a relatively short growing season. One of the largest barriers to successful organic reduced tillage is termination of the cover crop. We will perform cover crop trials at two research stations (WSU Puyallup and WSU Mount Vernon) during each year of the grant. We will measure above-ground biomass and carbon to nitrogen ratios of different varieties and mixtures, and will also consider timing for termination and compare termination methods (roller/crimper vs. flail mower) for grain cover crops.
• Develop and analyze strategies for long-term continuous reduced tillage in organic agriculture: To date we have not experimented with continuous reduced tillage methods in northwest Washington. We implement annual fall tillage to prepare the ground for winter cover crop seeding. However, we see the ability to eliminate fall tillage as an important next step to soil quality improvement which has been shown to occur over the long-term. We will measure soil quality indices (e.g. penetrometer, bulk density, chemical properties, and soil fauna) and weed populations in this treatment and the other 5 treatments in the long-term reduced tillage experiment.
• Provide essential support to 15 western Washington organic producers implementing reduced tillage techniques on their farms. Our surveys show 25-30% of respondents have tried some form of reduced tillage, but only 2 or 3 farmers in our stakeholder base have adopted the techniques we have studied. We will increase the number of commercial farms adopting these techniques through farmer recruitment at our events, and allowing farmers the use of our equipment.