Tracking Vegetable Yields and Labor in a No-Till Perennial Clover Living Mulch System

Progress report for ONE22-411

Project Type: Partnership
Funds awarded in 2022: $14,880.00
Projected End Date: 04/30/2024
Grant Recipient: Sawyer Farm
Region: Northeast
State: Massachusetts
Project Leader:
Lincoln Fishman
Sawyer Farm
Expand All

Project Information

Project Objectives:

The project seeks to identify key factors that affect soil health, vegetable yields, and labor in a perennial clover living mulch system (PCS).  

  1. For each crop (cabbage, winter squash, and paste tomatoes), we will identify the smallest plug size growers can use without experiencing yield drag. 
  2. For each crop, we will identify whether mowing clover according to variable high frequency versus variable low frequency affects yields, and track labor across both mowing regimens. Our data will provide information to guide growers in determining the appropriate mowing system for their operation.
  3. Each crop will have an organic, tilled control that will allow us to measure labor and yield differences between PCS and the control. This data will empower farmers to make informed economic decisions about PCS. 
  4. Comprehensive soil health assessment (Cornell CASH) will be compared (which includes SOC, SOM, soil respiration, active carbon, soil protein index, and other physical, chemical and biological indicators of soil health and fertility). Baseline tests will be collected in October of 2022, and tests will be taken in each treatment (PCS and tilled control) at the end of the 2023 season to provide initial information regarding carbon capture and nutrient retention in PCS versus control plots.

Organic no-till is in its infancy. Despite significant research efforts, organic no-till systems have yet to be adopted in any meaningful way. At Sawyer Farm, increasingly intense rainfall events led us to search for less tillage-intensive alternatives to the cover crop-based systems we’d been using since 2010. Despite rigorous cover-cropping regimes and various tillage-reduction techniques, we had unacceptable levels of erosion on our sloping vegetable fields. In the last few years, I have become very involved in a number of no-till farmers’ groups, and have reached out to dozens of academics and researchers to help find reduced tillage solutions that might work for Sawyer Farm. The results of this research have confirmed that we are not alone in our search, and that many, or even most, vegetable growers struggle to find no-till/low-till systems that fit their farm. 

We first tried transplanting into rolled rye, a system developed at the Rodale Institute, in Kutztown, PA. It was difficult to establish rye early enough, because most of our crops are still in the ground in September, and because rye does not reach anthesis in Western MA (zone 5b) until mid-June, which is after most of our crops need to be established. It generally requires an annual tillage event, to establish rye after crop harvest, which means that we had bare soil right at the time of year when increasingly intense hurricane-driven rain events are most likely.

We then tried tarping – widely used at other small farms in our area – but it requires an amount of labor that makes it unprofitable for most of our crops (we mostly grow low-value storage crops like cabbage, onions, and carrots). It also trades tillage for plastic; the solution we’re hoping for won’t require this trade-off in terms of externalities. 

Finally, we had success with a modified transferred mulch system, but the amount of hay needed puts a natural limit on the scalability of that system (it takes a minimum of five acres of hay to adequately mulch one acre of vegetables). To scale the system would have meant huge inputs of hay grown off-farm. That system also has mechanization problems – there is no transplanter that will reliably perform in 6-8” of hay mulch. 

My initial interest in transplanting into perennial clover came out of a decade of experience with undersowing Dutch White clover into established crops. We wondered if it would be possible, instead of plowing down the clover before spring planting, to transplant directly into it. I found an abundance of academic research regarding clover living mulches (detailed in the Previous Work section), but none that described an actual production system. I couldn’t find any farmers using a perennial clover system (PCS), until I came across a blog from Pittsburgh-area farmer Erik Koperek, who generously spent many hours on the phone giving me advice. 

In 2020 and 2021, we began implementing PCS. Though not every crop and every experiment has been a success, PCS has worked extremely well in many cases and is well worth pursuing. It vastly reduces the negative soil health impacts of tillage; is well-suited to the Northeast’s growing conditions; and, while unlikely to lend itself to certain crops (e.g. direct-seeded carrots), we feel confident that, with modifications and improvements, it can work for nearly all transplanted crops, and possibly large, direct-seeded crops as well. It requires little in the way of equipment, and offers a seasonal flexibility that is appealing to growers. It is a very scalable system – a one-acre grower can use a $15 bulb auger and a lawnmower, while a 100-acre grower could use a no-till transplanter and a row-mow unit. Most importantly, PCS requires only one tillage event every five years, to renew the clover stand.

However, competition between the clover and the cash crop can lead to yield drag. This competition and the resultant yield depression is the recurring theme of academic papers on perennial clover living mulches. Some of that loss can be minimized by system modifications, such as plug size and mowing frequency (the subject of the proposed study), and some can be compensated for by reduced labor costs (which we propose to track across PCS versus tilled controls). Plug size is critical – the larger the plug, the more aggressively the transplant can compete with clover during the crop's establishment phase. On the other hand, larger plugs require more greenhouse space, more potting soil, and reduce transplanting efficiency. Correlating plug size and yield would allow us to identify the minimum plug size needed for success. Mowing also reduces the competitiveness of the clover and thus increases yields. On the other hand, each mowing event adds significant labor. 

To my knowledge, transplant size has not been studied in a perennial clover living mulch system, though in our experience this factor is critical to success. Mowing has often been studied (see Previous Work), but the frequency seems to be chosen arbitrarily -- once versus twice; twice versus four times, etc. As a farmer, I know that every management technique is highly specific to the crop and the season. Arthur and I have developed two data-driven mowing regimens that would be useful in guiding farmers' attempts to implement PCS (please see Materials and Methods for details). 

Our goal is to gather data to help growers make their own decision about whether PCS could work for their crop mix, land base, and labor conditions (please see Outreach Plan). 

Most producers operate on extremely tight margins and are loath to try new systems while juggling loans, payrolls, and overhead. Growers like Trip Shaw, Partner Farmer on this project, immediately recognize the potential benefits of PCS, but need hard data on yield drag, baseline suggestions for plug size and mowing regimens, and labor assessments in order to justify their own trials. Trip’s excitement and hesitation is representative of the reception we’ve had so far to PCS. Four Corners Farm typifies the small- to mid-scale Northern growers that we would target for dissemination of this study’s results.


Click linked name(s) to expand/collapse or show everyone's info
  • Caro Roszell - Technical Advisor (Educator)
  • Trip Shaw - Producer
  • Arthur Siller - Technical Advisor (Researcher)


Materials and methods:

Field Site (Objectives 1, 2, 3, and 4)

The field at Four Corners Farm is Peru and Marlow fine sandy loam. Until 2017, the field was in conventional silage corn-on-corn. From 2018-2021 it was fallow. In the fall of 2021, the field was plowed and seeded to rye. In 2022, the field will grow vegetables and be undersown with clover in July. If we are selected for this grant, baseline soil health will be assessed in the fall of 2022 following the Cornell CASH system (see Supporting Materials), and 1/3 acre of the field will be selected for 2023 trials.


Experimental Design (Objectives 1 and 2)

Both experiments will explore vegetable production in a perennial clover living mulch system (PCS). In the spring, vegetables will be planted into the clover to explore the relationship of transplant plug size (Objective 1) and clover suppression (Objective 2) to vegetable yield. Labor time for clover mowing and weeding for PCS vegetable production will be compared with organic bare-soil production in control plots (Objective 3). 

For each of three vegetable crops (cabbage, winter squash, and paste tomatoes) a 500-foot bed will be planted in Dutch White clover (to be established in July, 2022), and another in bare soil. These crops have been selected for their diversity in terms of families and growth habits. The PCS and bare soil plots will be grown as close together as possible in order to minimize in-field variability, and will have identical crop histories. 

Each vegetable crop will be planted in a split-plot randomized complete block design with three blocks. Suppression level will be the main plot and plug size will be the subplots.

There will be two suppression treatments, high and low. The first maximizes suppression by mowing clover before its regrowth/recovery period has been achieved. Recovery periods vary by temperature, moisture, and nutrients. On-farm observations indicate that full recovery can occur within as few as ten days during early spring growth, whereas mid-late summer recovery times can take a month or more. In this treatment, clover will be mown at a height of 4", well before the Dutch White clover reaches its 6"+ maximum. (This treatment is referred to as high suppression in the "Layout" upload in supporting materials.) Mowing frequency will thus vary according to clover recovery times. The second suppression treatment is also variable frequency, but is less intensive overall (This is referred to as low suppression in the "Layout" upload.) Mowing will occur according to the ratio between clover height and crop height. The clover will be mown when its height is greater than 1/3 of average crop height (or width, in the case of squash). This treatment may require more frequent mowing during crop establishment, depending on the season, but mowing will cease when crops reach ~18" in height or width (Dutch White clover growth typically peaks at 6"). These mowing treatments are in contrast to fixed-frequency mowing treatments found in LM research, and aim to quantify Sawyer Farm's on-farm PCS management system. 


Agronomic Management (Objectives 1, 2, 3, and 4)


Tomatoes and winter squash will be planted in one row per bed at 24-inch in-row spacing. Cabbage will be planted in two rows per bed at 20-inch in-row spacing. Thus each subplot will have 10 tomato or squash plants or 24 cabbage plants. The plants will be started in the greenhouse between 2 and 8 weeks before transplanting in late May, as follows: Squash 2 weeks (72 tray), 3 weeks (48 tray), and 4 weeks (2.5" pot) prior to transplanting. Cabbage 5 weeks (72 tray), 6 weeks (48 tray), and 7 weeks (2.5" pot). Tomato 6 weeks (72 tray), 7 weeks (48 tray), and 8 weeks (2.5" pot). 


Dutch white clover will be mowed before transplanting and bare-soil plots will be tilled in preparation for transplanting. To plant into clover, a no-till transplanter will be used if varying plug sizes can be accommodated. Otherwise, various sizes of bulb augers on a cordless drill will be used to create transplanting holes. Tilled controls will be transplanted using traditional bare-soil techniques.


Following transplanting, clover suppression treatments will be implemented by mowing the clover according to low/high treatments shown in the treatment layout. A push lawnmower and string trimmer will be used to do the mowing. Bare-soil control plots will be cultivated with tractors, or by hand, as needed. In the bare-soil plots, the number of cultivations for each crop and the average cultivation time during the growing season will be recorded so that the weeding labor time in bare-soil plots can be compared to both clover suppression treatments. 


The vegetables will be fertilized with organic fertilizers following the initial soil test recommendations. 


All plots will be observed weekly to note any differences in pest pressure or growth habit and qualitative notes will be collected to document any farm-scale issues, plot, or treatment differences. Any insect or disease control measures that are needed will also be noted. 


The vegetable crops will be harvested in the early fall. Each crop will have a single harvest (except paste tomatoes, which will require 4-6 harvests) and the vegetables from each plot will be weighed to quantify the yield in each of the treatments.


Data Analysis (Objectives 1 and 2)

The yield of each crop will be statistically analyzed as a mixed effect model with main effect explanatory variables of clover suppression and plug size as discrete fixed effects. Block will be treated as a fixed random effect. Total yield and average fruit weight (or cabbage head weight) will be the response variables. If significant, differences between plug size treatments will be explored through mean separation using Tukey's HSD tests.


Comparison of PCS and bare-soil production (Objective 3)


The best performing PCS treatments for each crop will be compared with standard bare-soil production methods in terms of yield variables, labor time, logistical complexity, soil health assessment and any other differences which are noted during the course of the experiment. These comparisons will not be statistically analyzed since it is not possible at Sawyer Farm to randomize bare-soil and PCS plots. The differences in crop yields will be considered with differences in labor time, soil health, or other production issues such as the additional greenhouse time and space needed for large plug sizes. These differences will be quantified in terms of real on-farm costs and crop sales prices to determine a per acre economic impact of cabbage, tomato, and squash production in Dutch white clover.


Soil Health Comparison (Objective 4)


Following the harvest, composite soil samples will be collected in collaboration with American Farmland Trust from both living mulch plots and tilled plots and sent to Cornell University for Comprehensive Assessment of Soil Health in PCS and bare-soil plots. Penetration resistance will be measured in the field and twenty 8-inch deep, 1-inch wide soil cores will be collected from both growing systems. These composite soil samples will be analyzed for soil pH, organic matter, wet aggregate stability, active carbon, total carbon, total nitrogen, and total protein.

Research results and discussion:

2022 annual report:
We're on track so far. Caro took soil samples in October. I've found someone to do the data collection/fieldwork for next season, and I'm meeting with them, Caro and Arthur  to finalize experimental design and make a calendar together. 

I also spoke twice at NEVF, had a front-page article in NOFA's Natural Farmer, was on a CISA podcast, will be speaking twice at NOFA-MA's winter workshop, and twice at the Madison, WI Organic Growers Conference. In each of these articles/talks, I've highlighted the SARE grant as the natural extension of the on-farm research we've been doing the last couple years. I've used these opportunities, and lots of conversations with ag professionals and other farmers, to make sure that the information we're gathering in the SARE grant is just what farmers want to know before trialing perennial clover. 

There's lots of excitement about perennial clover in general and the results of this study in particular. 

Participation Summary

Education & Outreach Activities and Participation Summary

1 On-farm demonstrations
2 Published press articles, newsletters
3 Tours
6 Webinars / talks / presentations

Participation Summary:

200 Farmers participated
50 Number of agricultural educator or service providers reached through education and outreach activities
Education/outreach description:

Our project’s results would be shared with six organizations active in tillage reduction education. Each of them is aware of the work we’ve done with our transplanted vegetables in perennial clover system (PCS) since 2020, and has offered a platform for dissemination. Each has provided a letter of support, which I foolishly solicited before realizing that there is no upload section for Letters of Support on this grant. I have included them in the Supporting Materials. Although I understand the reviewers may choose not read them, I believe they indicate the level of interest among academics and soil advocates alike.

The first three organizations are farmer-to-farmer groups whose events I attend and contribute to, facilitated by non-profits and universities. I have spoken about PCS with these groups, and growers’ strong interest mingled with their strong hesitation is the impetus for gathering the data proposed in this grant. 

Methods, data, and discussion would be shared with these groups. I will offer free farmer-to-farmer consulting for any grower who wants to trial PCS. 

Caro Roszell (key collaborator) and Julie Fine of the climate and agriculture team at American Farmland Trust convene a practitioner network for growers interested in tillage reduction and cover cropping across New England with an active western Mass hub. I would speak to this group at one of our education events.

Claire Strader, Small-Scale and Organic Produce Educator at University of Wisconsin, organizes a monthly meeting of mid-Western growers exploring tillage reduction, and has invited me to speak to that group again.

Seva Tower, Marketing and Community Outreach Coordinator at the Hilltown Community Development Corporation, organizes winter meetings of growers in our region of Western MA. Trip Shaw and I are regular attendees and would present our findings.              

I have never had the opportunity of attending the annual winter meeting of the Ecological Farmers Association of Ontario, but Ken Laing, Farmer/Researcher for the Ecological Farmers Association of Ontario, has been a source of inspiration and wisdom through this process, and has invited me to share our results at that meeting if we are awarded this grant. 

Margaret Christie, Special Projects Director at Community in Support of Agriculture, has written a letter of support indicating ways that she and I will work together to disseminate this study’s results with Massachusetts growers. CISA offers a huge range of information and events for MA growers, and Margaret's letter of support indicates CISA’s willingness to aid in dissemination as their calendar of events for 2023 comes into focus. 

Sam Malriat, Director of Organic Consulting at the Rodale Institute, has been a source of no-till information and encouragement, and has invited me to share our results with Rodale’s consulting team. 

Overall, these efforts will conservatively reach 100 growers in direct, farmer-to-farmer settings; a greater number of growers indirectly via CISA’s network; and important stakeholders at the Rodale Institute, which continues to be a major player in tillage reduction research. 

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.