Use of Tarps to Terminate High-Residue Winter-Hardy Cover Crops Before No-Till Organic Vegetables

View the project final report

Commodities

• Vegetables: brussel sprouts

Practices

• Crop Production: cover crops, no-till
• Production Systems: general crop production

A common criticism of organic agriculture is that it relies too heavily on tillage. While there has been some success with cover crop based reduced tillage in organic no-till row crops like soybeans, no-till systems for organic vegetables are still a conundrum. Inadequate weed control, narrow cover crop termination windows, planting delays related to cover crop termination, and the need for specialized equipment are all challenges. This project was designed to address these issues by using tarps to terminate a high-residue winter-hardy mix of rye and vetch thus creating an in situ mulch suitable for no-till planting of organic vegetables. While a rye/vetch mix can provide a balance of hardy residue for mulch (rye) and nitrogen for vegetable development (vetch), successful termination of this combination can be tricky using organic methods. Successful roller crimping or mowing require that the covers are in flower, but rye and vetch are not often in sync when it comes to flowering and thus one or both can grow back after crimping or mowing. Additionally, waiting for the optimal termination window can delay vegetable planting. In this trial, tarps were used to terminate the cover crop, thus removing the need for a roller crimper, allowing for flexibility in timing, and creating a stale planting bed through occultation. Brussels sprouts were then no-till planted into the residue.

Key Findings

• Silage tarps and landscape fabric terminated the rye/vetch cover crop fully in three weeks.
• Brussels sprout yields were the same for all the no-till treatments and the conventionally tilled control.
• A good stand of rye is critical for creating a weed-smothering mulch layer.
• Labor was significantly higher for the tarped no-till treatments in this trial because of the hand-labor required for planting and because of insufficient cover crop biomass to prevent weeds.

Objective 1:  Assess the effectiveness of three different types of reusable tarps in terminating a rye/vetch cover crop before no-till organic vegetables

We tested 5ml black/white silage film, 6ml black/white bunker cover, and black landscape fabric in a randomized complete block design (RCBD) at four farms.  We collected data on cover crop and weed population counts, biomass, and percent residue coverage (using the line transect method.)

Objective 2:  Evaluate the yields and management costs of the no-till systems compared to a conventionally tilled control.

We tracked labor time, plant survivorship, and Brussels sprout yield.   An analysis of variance (ANOVA) was conducted using the R package lme4 (Bates et al 2015).  Means and 90% confidence intervals for each treatment were calculated with the R package emmeans (Lenth 2018).  A confidence level of 90% was used, meaning that for each comparison that is statistically significant, we are 90% confident that the difference is due to the treatments and not to chance variation.

Objective 3:  Share information with growers through a field day in 2018 and through a conference presentation.

We held a field day at Two Onion Farm 9/13/18.  The 14 attendees toured the trial plots, received a handout with the results to date, and discussed pros and cons of organic no-till.  We also presented at a session on organic vegetable no-till at the Organic Vegetable Production Conference on 2/2/19 to 95 attendees.

Objective 4:  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.

A farmer bulletin was completed and distributed in June 2019.  See information products.  The video is still in production and will be distributed in July 2019

Objective 5:  Contribute information to the development of longer, multi-year reduced tillage vegetable rotations

Results of the project were used to draft farmer recommendations for organic no-till tomatoes and distributed through the bulletins and videos.

References:

Bates, Douglas, Martin Maechler, Ben Bolker, and Steve Walker. 2015. Fitting linear mixed-effects models using lme4. Journal of Statistical Software 67(1): 1-48. doi:10.18637/jss.v067.i01.

Lenth, Russell. 2018. emmeans: Estimated Marginal Means, aka Least-Squares Means. R package version 1.2.3. https://CRAN.R-project.org/package=emmeans