- LINCOLN FISHMAN
Growing Vegetables in a Perennial Clover Living Mulch: Sawyer Farm’s Tillage Reduction Journey
BY LINCOLN FISHMAN
Sawyer Farm is in the Hilltowns of Western Massachusetts. We've been farming here since 2010. In the early years, an aggressive regime of cover cropping and applications of homemade compost helped build up soil health. However, the whole farm is on a slope, and, while contoured beds reduced erosion, they didn't eliminate it. In particular, increasingly intense rain events in the fall (the tail end of hurricanes moving up the coast) were causing visible erosion. These rains were coming in the critical period when fall cover crops were getting established and didn't provide full soil protection. Still, our cover cropping and manure applications seemed to compensate and soil health improved year over year until 2015.
It took us a while to reach the obvious conclusion: the frequency and intensity of our tillage were causing systemic damage and the cover crops and compost were just our annual apology for the damage we'd done.
Still, recognizing the impacts of tillage and actually moving towards tillage reduction are two different things. We manage five acres of vegetables, mostly storage crops with a relatively low price per pound. Five acres is tiny in the scheme of things, but enough that many small-scale, no-till systems seemed impractical for us in terms of labor or materials. (I'll spare you the full story, but we've experimented with tarps and transferred mulch, and still use them for certain crops.) Crimped rye is scalable, but rye doesn’t reliably reach anthesis until mid-June for us, so it was only a solution for a few crops.
We initially settled for a partial solution. We tilled in the spring, got our crops established, and then broadcast Dutch White clover into standing cash crops in July, after the last cultivation or once weeds were well controlled. (Alliums, brassicas, Solanaceae, cucurbits, corn – everything but storage carrots/beets and salad greens.) The clover provides 100% soil cover by late August, in time to protect the soil from fall rains. The clover overwinters, greens up in early spring, and is easy to incorporate before planting. This system is low labor, requires no new equipment, offers many soil health benefits, and the clover seems to have no negative impact on cash crop yields. Though Dutch White doesn't produce as much biomass or reach down as deep as many other cover crops, it is, in our experience, much easier to manage on a farm growing a diversity of crops, because it requires much less planning than other covers.
[Dutch White clover is the type of clover you see in lawns or overgrazed pasture. It is low-growing - rarely over 8". Other types of clover can work undersown with certain crops (e.g. red clover under corn), but Dutch White, because it is so short, offers much less competition and requires little to no mowing. It spreads aggressively through stolons, so it effectively suppresses weeds.]
After a number of years of undersowing Dutch White clover and discing it in the spring, we asked ourselves what, in retrospect seems, like an obvious question: Would it be possible to grow vegetables directly in clover? We doubted it--it seemed like the clover would provide too much competition for a little transplant, but we began doing research and found some university studies looking at transplanted vegetables or direct-seeded corn in perennial clover with exciting but mixed results. What we didn't find was any growers using the system.
In the spring of 2020, we ran a small experiment to test the viability of transplanting crops directly in established Dutch White clover. We put cabbage, squash, and hemp transplants into a 1/10 acre piece of clover that we had established the year before. We mowed the clover short with a lawnmower, used a bulb auger on a cordless drill to make a little hole, threw in a transplant and a handful of compost, pulled a line of drip tape down each row, and walked away. The clover immediately regrew and seemed to dominate the transplants. Oh well. We nearly forgot about our little experiment as we got busy with the ‘real’ crops. I occasionally noted that the transplants in clover hadn't actually died. They were even growing a little. But by mid-July, it was undeniable--those crops were really growing. At harvest, the cabbage heads were equivalent in size to the bare-soil cabbage in the next row over. The hemp was somewhat smaller than the bare-soil hemp, but the flowers were denser and slower to succumb to mold. The squash yield was unimpressive, but all-in-all, we were very pleasantly surprised. We'd avoided any kind of tillage in that experimental section, gotten good yields on two out of three crops, and hadn't done any work between transplanting and harvesting. We were excited to keep experimenting.
In 2021, we expanded the experiment to 1/2 acre and included more crops, but the weather conspired against our experiments. The spot we'd chosen doesn't drain well--fine in a normal year, but disastrous in 2021, when we received 16 inches of rain in July and more and more and more after that. Few crops--whether in bare soil or in clover--did well that year, so we didn't learn much. We certainly did notice, however, that there was no erosion in the clover plots.
For 2022, we got a grant for a Mechanical Transplanter. (The bulb auger works really well, but is too slow for multiple acres of transplants.) We put a coulter and an aggressive ripper tooth ahead of the planting shoe to open and loosen a small furrow for the transplant. We had to add a lot of weight (~250 pounds) to the packing wheels to effectively close the furrow, and then counterweight the drive wheel to get good ground contact. (I won't get into lots of detail here, but I am happy to share the nitty gritty--please contact me if you're interested.) In the end, the transplanter created a 6-8" wide furrow and effectively set the transplants. We were able to run the transplanter just about as fast as in bare soil, making transplanting into clover at scale a reality.
Here's a rundown of which crops worked and which didn't in 2022.
Brassicas - cabbage, kale, collards, broccoli
Multiple varieties of cherry and beefsteak tomatoes
Ace red peppers
(Neither made much fruit. They seemed to suffer from either low soil temps or clover competition.)
Successful, but with a caveat:
Direct-seeded dry beans did well, but need to be harvested in a timely manner because the clover creates a damp environment around the pods as they dry down.
Summer squash yielded less per week than summer squash successions on plastic, but produced all season long.
Poblanos and hot peppers took a long time to produce (lower soil temperatures under clover?) but made a respectable crop after all.
Butterhead lettuce transplanted 6/1 grew nicely and was slow to bolt, but was unmarketable due to slug damage. More upright Romaine-type lettuce might do better, or later successions in the warmer, drier months.
Food for thought:
When we broadcast the clover, we often mix it with our chicken feed--a mix of cracked grains. Sometimes whole barley kernels make it through the grinder. A number of these managed to germinate this spring and made nice seed heads. Next year, we'll explore whether drilling barley and oats into the clover in spring is a possibility.
We have a lot of faith in this system at this point, and will greatly expand it in 2023, though it is very much in development.
Here are its current limitations:
1) Crop limited. We believe there are certain crops that will never thrive in perennial clover, such as small, slow-growing direct-seeded crops like carrots. Some transplanted crops, like onions, we haven't experimented with, but we think will not be competitive enough.
2) Cool soil temperatures. Compared with plastic or bare soil, perennial clover shades and cools the soil. It is hard to imagine that it will ever be a good system for early production in the Northeast.
3) Transplanter modification issues. The planting shoe made a furrow that slowly filled in with weeds. Within a few days after transplanting, the clover on either side of the furrow regrew quickly and canopied over the furrow, but weeds did germinate in the furrow. Though they were slow to grow, the weeds finally emerged and took off in late July. We mowed and weed whacked a couple of times to control weed growth. Weeds were much less of an issue when we were using the bulb auger. Creating less disturbance is possible, but will require modifications.
4) Yield reduction. While some crops do not seem to exhibit any yield drag in clover, others do. It is difficult to quantify this loss as it varies so much depending on the season, the variety, etc. For us, some yield loss is economically and/or environmentally justified because of the many benefits of the system.
Benefits of the perennial clover system:
1) Soil health and ecosystem services abound! Eliminates tillage and erosion. Clover feeds the soil biology all year round. Carbon is captured, rainfall infiltrates easily, and moisture is kept in the soil through shading. Pollinators specifically and insects generally are present in huge numbers. Introducing a perennial into our production system leads to stability in the soil community that cannot be achieved in an annual system.
2) Reduced pest pressure. Aside from slug damage on lettuce and some cabbage worm damage on cabbage, there were few pest issues and we didn't use row cover on any crops.
3) Clover fixes N, which saves on fertilizer.
4) Labor and fuel savings. Even with additional mowing/weed whacking because of weeds in the planting furrow, the labor per acre was lower than bare-soil cultivation. In between transplanting/seeding and harvesting, the tractor makes zero passes over the field.
5) Pleasant to work in and around. Harvesting in clover is a pleasure. Never dusty, never muddy. The harvest crew is always standing or kneeling on a lawn of clover. The biological diversity inherent in this system is aesthetically very pleasing. Unlike in bare soil, you can lay down anywhere in the clover field and watch hundreds of insects interacting with each other, the clover, and the crop. The field feels and is alive and vital.
There's so much we don't know about this system yet, both because it's new and because it's a living system that is inherently far more complex and dynamic than growing in bare soil or on plastic. Water and nutrient dynamics are still a bit of a mystery to us. The clover seems to compete for water during crop establishment, but later in the season, it appears to help conserve moisture through shading. Does it help dry out the soil in spring through transpiration? What is the N contribution of the clover in its first year of establishment? Second year? Etc. Does mowing the clover release N for the crop? In what time frame? Does the clover reduce leaching and allow nutrients to persist for longer in the soil? Does it compete for nutrients with the cash crop? If so, which ones? And so on!
Having all these unanswered questions can be a headache. I definitely started farming with a “straight rows, clean fields” mentality. I often failed at that, but I knew what we were aiming for. There was a smaller set of variables. Making the shift to clover has been a real trust exercise. I’m always having to remind myself to be less controlling and put more faith in complexity and diversity. Honestly, it took more mental effort to stop worrying about weeds in the clover than the physical effort it used to take to actually weed!
Now I try to remind myself that these unanswered questions are a good thing. The more complex and biodiverse the agricultural ecosystem is, the more questions there will be. There are more connections and interactions, and more stability and resilience. Giving up control, trusting nature, embracing uncertainty – I think those are things that every farmer has to learn pretty quickly. We are constantly reminded to be humble and are frequently graced with wonder. That seems to be the main kind of compensation we get in this line of work.
How long does the clover persist?
In our limited experience, the clover forms a solid stand for about three years. In the fourth year, perennial grasses and forbs begin to get a foothold, though crops can still thrive. In year five, the clover field begins to resemble pasture, and needs to be plowed down and re-seeded (or grazed/hayed/fallowed). This season, we plowed and cover cropped a half acre that was sown to clover in 2018. In 2023, it will grow bare-soil crops, undersown with clover. So this is not truly a no-till system, but it does make tillage rare. Once it's fully established on our farm, we imagine that, in a given year, 75% of our acreage will be clover, and 25% will be bare soil. It's possible that with more frequent mowing and more careful applications of lime and sulfur, the clover could persist for longer.
For 2023, we've received a SARE grant, in partnership with American Farmland Trust, Arthur Siller, PhD candidate at UMass School of Stockbridge, and our neighbor, Trip Shaw, at Four Corners Farm. We will gather data to do an economic and soil health analysis of the perennial clover system versus a bare soil control. We hope this data will help point the way for growers interested in trialing this system who need hard data on potential yield losses versus labor/fertilizer/fuel/soil health savings.
We’ll also be further modifying the transplanter to reduce weeds in the furrow, and expanding the number of crops we're experimenting with.
The real next step for us is working with other growers who think this could be an exciting tillage reduction system for their farms. Ultimately, we hope to be part of a network of growers with problem-solving scalable no-till solutions together.
If you're interested in learning more about growing crops in a perennial living clover mulch, please contact Lincoln at firstname.lastname@example.org or at 413-320-8535.