Expanding No-till Organic Vegetable Production through the Combination of High-residue Cover Crops and Solarizing Tarps

Progress report for LNE18-371R

Project Type: Research Only
Funds awarded in 2018: $126,668.00
Projected End Date: 11/30/2021
Grant Recipient: University of New Hampshire
Region: Northeast
State: New Hampshire
Project Leader:
Dr. Richard Smith
University of New Hampshire
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Project Information

Project Objective:

This novel system has both agro-ecological and socio-economic knowledge gaps. Our objective is to address both. To assess the ultimate adoptability of the CCTNT practice, we will first investigate the extent to which it provides increased ecosystem services, specifically yield, weed suppression, and soil health, as well as the costs of implementing the system. With this information, we will assess whether farmers are willing to adopt this system and their valuation of individual components/attributes of the system (e.g. increased soil health vs. the use of plastic) using a discrete choice experiment that will guide outreach efforts and future research.

Introduction:

Cover crops and no-till are management practices that can improve soil health, but their implementation in vegetable production systems remains limited, particularly in cooler climates like New England with shorter growing seasons. While cover crop use is increasing, most vegetable farmers terminate them before peak biomass because of challenges associated with residue incorporation and nutrient immobilization.This project aims to address the limitations of no-till and cover cropping in a scale-appropriate way for vegetable farmers in the Northeast by using reusable plastic tarps. Small-scale vegetable farms represent a critical part of the agricultural landscape in the Northeast. There are 458 certified organic vegetable farms in the six New England states and 4,126 small vegetable farms (growing 0.1-4.9 acres of vegetables). 

Tarps are an increasingly popular tool for many small-scale growers and are mostly used to augment stale seedbedding with bare soil. We have applied the concept to terminate cover crops and facilitate no-till transplanting. Tarps enable flexible timing of cover crop termination while providing additional weed suppression and possible benefits of increased N mineralization. For short, we call this system CCTNT (cover crop-tarp-no-till), and our initial field trial in 2016 using this system showed that tarps effectively terminate cover crops and increase cabbage yields compared to a mechanically terminated cover crop. 

Cooperators

Click linked name(s) to expand
  • Jason Lilley (Educator)
  • Shadi Atallah (Researcher)
  • Natalie Lounsbury (Researcher)

Research

Hypothesis:
  1. Solarizing tarps improve the performance of high residue organic no-till vegetable production through effective cover crop termination, enhanced weed suppression, and improved nutrient availability and soil health.
  2. Benefits of tarping with respect to weed suppression and nutrient availability increase with longer tarp duration, but cover crops are terminated and weeds are mostly suppressed in as little as one week.
  3. Solarizing tarps and CCTNT systems will alleviate the economic and environmental constraints that currently limit small-scale farmer adoption of cover crops and no-till practices.
Materials and methods:

In 2018, we had two replicated experiments and five on-farm unreplicated experiments. The two replicated experiments were: 

Systems experiment looking at cabbage production after six different tillage and tarping combinations. The treatments were: no-till after mowed (sickle bar) rye-vetch; no-till after rolled rye-vetch that was tarped for four weeks; no-till after mowed (sickle bar) rye-vetch; mowed (sickle bar), tilled and tarped for four weeks; mowed (bush hog), tilled, and stale seedbed for four weeks, and mowed (sickle bar) tilled and stale seedbed for four weeks. The tarps were applied at the beginning of June and cabbage was planted at the beginning of July. During the season, the plots were split into weeded and unweeded subplots. Soil temperature and moisture were monitored. Cabbage yield and weed biomass was measured at the end of August. We also had two fields planted to this experiment in 2017.  

Tarp duration experiment looking at the tradeoffs between cover crop biomass production, weed suppression, mulch decomposition and nutrient mineralization at different tarp application times and durations. No crop was grown in this experiment. Three different tarp application dates and durations were investigated, in addition to a glyphosate control treatment on each tarp application date. 

Five on-farm experiments with farmer-led treatments included: cauliflower grown in three treatments including tilled soil with black plastic, tilled soil without black plastic, and no-till with an oat cover crop terminated with a tarp; broccoli grown in tilled soil vs. no-till in rye terminated with a tarp; acorn squash grown in sod terminated with a tarp that was either tilled or no-till; no-till cabbages grown in a rye clover cover crop terminated with a tarp; and mixed vegetables grown either in tilled soil or no-till rye terminated with a tarp. 

In 2019, we had one replicated experiment in Durham, NH of the tarp duration experiment. In addition to the glyphosate control, we had a roller-crimp only treatment on each tarp application date. There were three unreplicated on-farm experiments similar to 2018. 

We began focus groups with farmers to discuss their perceptions of cover crops, reduced tillage, and tarp use beginning in early 2020 with one focus group, but were delayed by Covid-19, the inability to meet in person, and the ensuing busy growing season. 

Research results and discussion:

We are still analyzing results from both years' (2017-2018, 2018-2019) experiments. However, response to the system from our farmer collaborators was mixed. Like many reduced tillage/no-till systems, it appears that initial soil quality and weed pressure can be a significant barrier to implementing this technique effectively. On one farm with heavier, compacted soils and where the cover crop growth was spotty, the broccoli crop performance was highly variable in the no-till treatment. Quackgrass competition and soil compaction appear to have been major limiting factors. However, on another farm with very high-biomass cover crops and sandy soil with high nutrient availability from extensive compost use, cabbage performance was not limited. The acorn squash planted directly into sod terminated with a tarp performed equally to the squash planted into tilled soil and there were almost zero weeds in both treatments. 

The variability in performance of this system is likely driven by innate soil quality as well as cover crop performance, which has a strong influence on weed suppression because it is directly correlated to the amount of surface mulch remaining. All farmers wanted to try this system again, despite the mixed performance. 

Although we are waiting for the results of ongoing replicated experiments to draw broader conclusions, we published a preliminary report in 2018 on the initial field trial that we conducted in 2015-2016 looking at clear vs. black tarps to terminate cover crops. Because this was a single site and a single season with some anomalous weather conditions (drought of 2016), further (ongoing) research is necessary to draw broad conclusions. However, we chose not to repeat the experiment in the same form based on the results, and instead to focus on the use of black plastic instead of clear: 

We no-till transplanted cabbage into a winter rye (Secale cereale L.)-hairy vetch (Vicia villosa Roth) cover crop mulch that was terminated with either a roller-crimper alone or a roller-crimper plus black or clear tarps. Tarps were applied for durations of 2, 4 and 5 weeks. Across tarp durations, black tarps increased the mean cabbage head weight by 58% compared with the no tarp treatment. This was likely due to a combination of improved weed suppression and nutrient availability. Although soil nutrients and biological activity were not directly measured, remaining cover crop mulch in the black tarp treatments was reduced by more than 1100 kg ha−1 when tarps were removed compared with clear and no tarp treatments.

 

Research conclusions:

Research is ongoing and we do not have conclusions to report. 

Participation Summary
5 Farmers participating in research

Education & Outreach Activities and Participation Summary

Educational activities:

10 Consultations
1 Journal articles
1 On-farm demonstrations
7 Webinars / talks / presentations
2 Workshop field days

Participation Summary:

500 Farmers
100 Number of agricultural educator or service providers reached through education and outreach activities
Outreach description:

Jason and Natalie presented a talk at the Northeast Cover Crop Council meeting in State College on November 15, 2018 with approximately 30 people (mostly ag service providers) in attendance. 

Natalie presented a talk on January 22, 2019 in Fairlee, VT at a workshop on "tarps and mulching." There were 150 farmers and a few service providers in attendance. 

We held a field day in Durham, NH on June 26, 2019 at our experiment site in conjunction with NRCS and conservation districts demonstrating available equipment for reduced tillage. An early afternoon workshop for service providers (NRCS) had 12 attendees. A later afternoon workshop for farmers also had 12 attendees. 

Nick Warren gave an of the experiment was given during a talk for New Hampshire Extension specialists on July 25, 2019. There were 26 people in attendance. 

Jason Lilley held a soil health field day at participating Bumbleroot Farm in Windham, ME on August 29, 2019 during which their on-farm experiment was discussed. There were 15 farmers in attendance. 

Natalie and farmer cooperator Daniel Mays both gave talks in a session on cover crops on low acreage and using tarps at MOFGA's Farmer to Farmer Conference on November 3, 2019 in Camden, ME. There were 50 farmers in attendance. 

Natalie gave a talk at the New England Vegetable and Fruit Conference in Manchester, NH on December 10, 2019 and there were 90 farmers in attendance. 

Natalie gave a webinar for the University of New Hampshire Integrated Pest Management webinar series on February 14, 2020. In addition to attendees, it has had 150 views online. 

Natalie gave a webinar for the University of Vermont Cover Crops and Reduced Tillage series on April 6, 2020. In addition to attendees, it has 100 views online.  

We are currently working with researchers and Extension personnel from the University of Maine, Cornell, and the University of New Hampshire to publish a comprehensive guide to tarping (online and in print), which will include information on the system investigated in this research project as well as others. It will include descriptions of how tarping works, different applications, and case studies of farmers using tarping in these different ways. Two of the case studies will be a collaborator on this project and a farmer who started using this system after hearing one of our talks.  

Another webinar is scheduled for growers through Washington State University on February 25, 2021. 

We published an article on our preliminary trial with the no-till tarp system in Renewable Agriculture and Food Systems titled "Investigating tarps to facilitate organic no-till cabbage production with high-residue cover crops" https://doi.org/10.1017/S1742170518000509

Learning Outcomes

10 Farmers reported changes in knowledge, attitudes, skills and/or awareness as a result of their participation
15 Service providers reported changes in knowledge, attitudes, skills and/or awareness as a result of project outreach
15 Educators or agricultural service providers reported changes in knowledge, skills, and/or attitudes as a result of their project outreach
Key areas in which farmers reported changes in knowledge, attitude, skills and/or awareness:

A farmer sent an email asking about transplanting tools to use in this system. After a discussing of what might work, he replied "Seeing your presentation a couple years ago was a real inspiration to try this different growing method.  After managing our farm for 8 years with intensive tillage and seeing problems proliferate, it's delightful for me to be able to grow crops in this way with excellent weed suppression, soil coverage, and reduced tillage." This system provides a way for farmers to integrate practices that they know are "good" for soil, but are sometimes hard to integrate (i.e. cover crops and reduced tillage), largely because of weeds. 

Information Products

Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.