One common criticism of organic agriculture is that it relies too heavily on tillage. While there has been some success with organic no-till row crops, organic no-till vegetables are still a conundrum. Inadequate weed control, narrow cover crop termination windows, planting delays related to termination, and the need for specialized equipment are all challenges. This project design will address all of those issues and will focus on the use of tarps to kill a high-residue winter-hardy mix of rye and vetch before organic vegetables. While a rye/vetch mix is commonly used in this type of system, successful termination can be tricky as the optimal termination windows for rye and vetch are not often in sync. In this trial, a disengaged rotovator will knock over and align the cover crop and tarping will be the primary termination technique, thus removing the need for a roller crimper, allowing for flexibility in timing, and creating a stale seed bed through occulation. For the sake of data collection, the vegetable crop will be Brussel sprouts. This research will also inform other transplanted vegetable crops. Organic vegetable farmers in south central Wisconsin will cooperate on this research, which will be relevant to the upper Midwest.
- Assess the effectiveness of three different types of reusable tarps in terminating a rye/vetch cover crop before no-till organic vegetables
- Evaluate the yields and management costs of the no-till systems compared to a conventionally tilled control.
- Share information with growers through a field day in 2018 (expected attendance of 35 to 40)
- Create an illustrated info sheet and short video with project results and recommendations to be posted on the Dane County Extension website and disseminated through our vegetable farmer database (240 addresses)
- Contribute information to the development of longer, multi-year reduced tillage vegetable rotations
Trials were established on four cooperating farms in southern WI. All the farms are certified organic and have between 8 and 14 years of experience with vegetables and cover crops. Prior to establishing the trial plots, two of the farmers used them as part of their normal spring vegetable production followed by buckwheat. In one case, the plot was planted to spring oats before the trial. And in the last case, living clover aisles established in 2015 were left in place without vegetables prior to establishing the trial. On all the farms, the preceding cover crop was tilled in 7 to 14 days before seeding rye and vetch.
On 7/25/17 three farms were seeded to rye and hairy vetch. Seed was broadcast onto the plots using an Earthway handheld broadcast spreader at a rate of 180 lb/acre for rye and 40 lb/acre for hairy vetch. Farmers tilled in the seed immediately after spreading to establish soil to seed contact. The last farm delayed seeding until 8/9/17 due to excessive soil moisture. In all cases the seed was watered in with either rain or irrigation within two days of seeding.
Rye and hairy vetch populations were counted 14 to 21 days after seeding in order to assess if they would provide an adequate stand. Research did not uncover a basic stand assessment by population count, so we calculated our own for rye: standard rye broadcast seeding rate of 75 lb/acre * 19,900 seeds per lb * our 85% germ rate / 43560 square ft/acre = 29 plants/square ft. One farm was far below the target of 29 rye plants/square foot and was reseeded and tilled on 8/9/17. Even on the other three farms, the rye population count was not where we wanted it to be, ranging from 15 to 24 plants/square foot. Overall the stands looked good, however, so instead of reseeding we scattered some extra seed over any edges or corners that looked thin.
In early November rye, hairy vetch, and weed populations were counted and biomass samples were taken on all farms.
Cover Crop Establishment
Visual assessment of the rye/vetch cover crop on all the farms was in line with what we expected by November 2017. The dry biomass measurements for rye in November, however, showed variability among the farms, ranging from 40 to 139 grams/square meter. Rye biomass is especially important for this trial because the rye residue is expected to smother weeds throughout the following growing season. Biomass measurements will be taken again in the spring before tarps are applied to kill the covers prior to planting Brussels sprouts.
Dry Biomass in grams/square meter on 11/1/17
Weed population counts taken 14 to 21 days after cover crop seeding in August ranged from 0 to 115 weeds per square foot across the four farms. Two farms clearly had fewer weeds with an average of 0.5 and 2 weeds per square foot. The two others had many more weeds with an average of 34 and 56 per square foot. Weed population counts taken at the end of the season showed a decrease on all farms, with a dramatic decrease on the most weedy farms.
2017 Weed Populations in plants/square foot
Educational & Outreach Activities
Cover crops were established in 2017. A field tour will happen at Two Onion farm in 2018 so farmers can examine the trials in person. Other education and outreach will happen after trial results are in.
Though cover crops are commonly used on organic vegetable farms, using them as a base for reduced tillage techniques is still an area for experimentation and is far from common. In fact, tillage is the primary termination method for over-wintered cover crops on organic vegetable farms, and organic farms in general or often criticized for the number of tillage passes they use. If this project is successful at using tarps to terminate an over-wintered rye/vetch cover crop and create a mulched bed for no-till planting, we will contribute important information to farmers on how to reduce tillage on their vegetable farms and thus improve soil quality.
Labor and yield data will be used to analyze the economic impact of this technique as well, and will be available in 2019.