Exploring innovations in climate resilient organic vegetable production systems through collaborative research and knowledge building

Objective 1: Assess agroecological outcomes for a cover crop based reduced tillage system with a focus on increased weed control and vegetable yield.

Roller-crimped rye is a go-to system for organic no-till row crop systems, particularly soybeans. Prior research by Dr. Erin Silva’s group has shown that in the Midwest, rye establishment by mid September is essential to grow sufficient biomass for successful crimping termination and weed suppression in the cropping year. (Note: to enable timely establishment of rye cover crops, if funded we will request a project start date of September 10, 2023.) Crimping at anthesis (flowering) crushes stalks, cutting off the flow of nutrients and water through the plant and creating a dense weed suppressive mulch. Rye will regrow if crimped too early. Rye residue ties up soil nitrogen, especially in the early stages of decomposition, so it is frequently planted with the legume hairy vetch to add nitrogen into the system. As with rye, crimping is more likely to terminate vetch if timed to coincide with flowering. Timing of rye termination is also critical for planting the vegetable crop. Vegetables that are planted after the last frost can be roughly timed with rye anthesis, but alternative termination methods such as occultation are needed for earlier vegetable planting.

Two replicated trials evaluating winter rye as an in-situ mulch will focus on weed suppression and vegetable production respectively. Our current research identified two key obstacles to on-farm implementation of this system: producing adequate rye biomass for weed suppression (objective 1a), and yield reductions likely due to inadequate crop nutrition (objective 1b). Additional takeaways were that perennial weeds cannot be managed effectively in a no-till system, and that rye in-situ mulch is best rotated with other reduced tillage approaches. For these reasons, these trials will be conducted at the West Madison Agricultural Research Station (WMARS), on organic-certified land managed with an on-going crop rotation system that offers appropriate windows for a trial of the crimped winter rye system. 

Objective 1a: Assess the effect of variety, vetch companion crop, and establishment technique on weed control by roller-crimped winter rye.

Rye maturity timing can significantly impact the success of roller-crimped systems, but cover crop seed is often "VNS" - variety not stated. We chose two early-maturing winter rye varieties, ND Gardner and Aroostook, that reach anthesis in late May to early June, for timing compatible with summer vegetable crops. The recently released ND Gardner is a promising alternative to Aroostook due to its earlier maturity, greater winter hardiness and greater biomass production. These two rye varieties will be planted on their own and with AU Merit hairy vetch. AU Merit is a newer early maturing hairy vetch variety, making it a good candidate for crimping with early-maturing winter rye varieties. 

We will compare three seeding techniques for cover crop establishment that span methods commonly used by farmers and methods that could be adopted with evidence of good results. We will compare the most common establishment method, (1) broadcasting into tilled soil followed by rototilling, to two reduced tillage methods, (2) broadcasting onto bare ground followed by power harrowing, (3) power harrowing before using a 3-row Jang seeder with double disc openers. Organic vegetable farmers commonly use tillage to improve soil-to-seed contact when establishing cover crops, and do not generally have access to no-till seeding methods. Power harrows are gaining popularity as a lower disturbance tool compared to rototillers. Seeders such as the Jang push seeder are primarily used with vegetable crops and are increasingly used for cover crops at small scale. While it is not considered suitable for no-till use, some success has been reported in low residue situations using Jang push seeders with double disc openers (eg SARE project LNE11-312). We chose the three row Jang as a balance between number of passes and ability to handle uneven ground. (Ideally we would also compare establishment with a no-till drill such as the compact 5- and 6-foot drills now available. However, equipment access is currently a limiting factor due to equipment cost and feasibility of scheduling/transporting rental equipment.)

All plots will be established in early September, using a split plot design with establishment method as the main plot effect and variety/seed mix as the subplot effect, replicated four times. A preceding cover crop of buckwheat, chosen for its fast growth and weed smothering ability, will be flail mowed prior to rye and vetch planting to simulate a low residue vegetable crop. Labor time for cover crop seeding will be recorded. Rye and inoculated vetch will be seeded at 180 lb/A and 20 lb/A respectively. Biomass of rye, vetch, and weeds (broadleaf and grass) will be measured immediately before termination with our small scale walk-behind roller-crimper (designed by USDA Agricultural Engineer Dr. Ted Kornecki and used successfully in our current research trials). Cover crop termination rate will be evaluated visually on a 0-100 scale one, two and three weeks after crimping. Cover crop residue cover (as regular points along a line) and weed population counts (within a quadrat at two locations per plot) will be recorded weekly, along with regular photographs, until late July, when plots will be mowed to prevent weed seed set. Soil samples will be evaluated for nitrates in late June and in October, when a final evaluation of cover crop residue will be recorded. Water infiltration rate will be measured with a single ring infiltration method in October. This trial will rotate onto new ground each year. 

Objective 1b: Assess the effect of cover crop termination method and supplemental nitrogen on cabbage yield in a rye-based no-till system.

CROVP group members report good results with fall brassicas in reduced tillage systems. In our previous trials of cabbage in high residue rye systems, however, we saw reduced yields and evidence of insufficient crop nutrition. We will test a range of nitrogen amendment levels in combination with two no-till termination methods  - roller crimping and occultation with landscape fabric - and a tilled control. Much like the establishment methods in objective 1a, these termination methods span what growers are currently using (tillage and occultation) and what they may move toward with evidence of good results (crimping). 

Rye will be drilled into tilled ground following a summer buckwheat cover crop, in mid September. ND Dylan winter rye was chosen for excellent winter hardiness and spring vigor in addition to medium-late maturity, suited to fall brassica planting time. The trial will be set up with a split plot design, with rye termination as the main plot effect, fertility as the subplot effect, and four replications. Rye in occultation plots will be rolled with a disengaged tiller (not crimped) and covered with landscape fabric for four weeks beginning in late May. Roller crimped plots will be terminated at rye anthesis, anticipated to be mid-June. Fertility amendments will be formulated to supply 140, 180 or 220 pounds nitrogen per acres and to meet crop phosphorus and potassium needs, and hand applied. Cabbage will be hand planted in early July. 

Biomass of rye and weeds (broadleaf and grass) will be measured immediately before termination. Rye termination rate, residue cover, and weed population counts will be taken weekly and prior to any weeding event, along with regular photographs. Labor time will be recorded for all activity in the plots including rye planting and termination, cabbage planting, and weeding (hand pull in roller crimped and occulted plots, wheel hoe in tilled control.) Soil samples will be evaluated for nitrates in late June and in October, when a final evaluation of cover crop residue will be recorded. Water infiltration rate will be measured with a single ring infiltration method in October. Yield and marketability data will be taken at harvest. After harvest, the plots will be mowed. This trial will rotate onto new ground at the research station each year. 

Objective 2: Facilitate farmer working groups within the Climate Resilient Organic Vegetable Production (CROVP) Community of Practice (CoP) to focus on reduced tillage techniques for diversified vegetable production.

As a research team with a strong record of participatory research, we will deepen our work with the CROVP CoP established through our 2019-2023 SARE project (LNC19-421). The CROVP CoP has discussed a number of reduced tillage strategies beyond the cover crop based system we are exploring in Objective 1. These strategies stand out because farmers are currently experimenting with them, and feel they have the basic equipment and know-how to do so alongside their established tillage-based systems. Even so, they have identified numerous areas where systems need to be improved, and identify peer-to-peer collaboration and joint learning as an effective path forward. As a collaborative research team, we see direct observation of systems on working farms as critical first steps in formulating hypotheses for future trials.

Working groups will be set up to innovate and problem solve through deeper peer-to-peer engagement with the systems outlined below. Working group topics emerged from group discussions with CROVP CoP members. Researchers will support the working groups by convening meetings and organizing farm visits and field days. Growers expect to communicate with each other directly multiple times through the season as questions and ideas arise. Growers and researchers will collaborate to develop simple methods to record system details and grower observations of field, soil, and crop conditions. Researchers will collate this information for sharing with the full CoP.  

1. Mechanizing cut-and-carry mulch systems. Many farmers in the CoP have ample land for their vegetable crops and are growing cover crops in separate fields for harvest and transfer to vegetable beds as mulch, a weed management strategy that reduces summer cultivation and soil disturbance and protects soil from erosion. Farmers identify the lack of specialized equipment for mechanized mulch transfer as an obstacle to scaling up this system, and are interested in approaches such as repurposing older equipment (eg self-unloading wagons, manure spreaders), organizing demonstrations of commercially available equipment, and learning from farmer-innovators such as Jan-Hendrik Cropp and Broadfork Farm (compost spreader). Growers will be supported in documenting and evaluating their current and evolving systems, including equipment details and modifications, management of cover crops grown for mulch, and system performance (as ratings) for labor and effectiveness. 
2. Managing multi-year rotations to reduce tillage. This group of farmers rotates vegetable production methods across multiple years to extend the time between major tillage events, recognizing that some soil disturbance is inevitable for harvest of root and tuber crops, and helpful for establishment of other crops. Growers will be supported in documenting their succession, timing, and techniques for managing vegetable and cover crops, with particular attention to seedbed preparation techniques, tillage frequency and intensity, and techniques and effectiveness of managing annual and perennial weeds.
3. Managing winter-killed cover crops in deep compost mulch systems. In this labor-intensive system permanent deep compost beds are established and “mulched” with 1-2” of compost before each crop. Farmers are wary of using cover crops in these high value beds but also want to mitigate the potential for phosphorus run-off in high rainfall events after heavy compost additions. This group will trial winter-killed cover crops such as oats, peas, or buckwheat, that have low potential to impede spring planting with remaining residue. Researchers will recruit up to ten farmers for trials, in addition to the two lead farmers (see letter). Farmers will be sent seed for up to four cover crop species or mixtures for establishment in late summer or fall. Farmers will be supported in use of the SeedLinked platform, commonly used for participatory variety trialing, to report management details and evaluations of cover crop establishment, spring residue cover, and ease of spring planting.   

We will produce a case study for each working group based on farmer interviews and documentation of systems, experimentation, and trial results. As the working group focusing on multi-year rotations that minimize tillage events will necessarily be more complicated, we will produce up to three additional and farm-specific case studies for this topic. Case studies will be reviewed by the appropriate working group and made available on our project website.