Minimum Tillage and Appropriate Machinery
The soil, good Quebec soil, contains within it fertile treasures. It wants nothing but to produce beautiful and plentiful harvests—but the farmer must also know how to treat it well for it to give all that it can.
—Adélard Godbout, Quebec Minister of Agriculture, Les champs, 1933
WHEN WE STARTED market gardening, the only tool we had for soil preparation was a rotary tiller (also referred to as a rototiller or tiller). And man did we use it! Back then it felt like the best invention ever. Just one passage with this machine would clean the soil of existing weeds and crop debris, while simultaneously preparing a smooth seedbed. The soil it worked was so loose that you could stick your whole hand into it. Eventually, however, as we became more educated about growing crops professionally and learned more about soil biology, we realized that although the tiller could rapidly prepare seedbeds, another intended result—healthy soil—was not actually happening. The tiller seemed to be doing all of that is desired in soil preparation, breaking up compaction and improving drainage, but its actual effect was in fact the reverse. Instead of building soil structure, we were undermining it in the long haul.
Because our first garden was on rented land, this wasn’t so much of a concern; the long-term health of the soil was less a preoccupation than our short-term need for practical simplicity. However, when we moved to our permanent site, it became obvious that we needed to improve our understanding of soil structure and rethink our tillage practices. It was Eliot Coleman who first pointed us in the right direction for developing surface cultivation techniques. In The New Organic Grower, one of our revered books at the time, Coleman describes his different tillage practices but also suggests that reducing tillage, or even eliminating it entirely, might prove to be the ideal way of growing great crops. He asserts, however, that the main challenge to the practice of non-tillage or low-tillage is preparing soil as efficiently as conventional tilling does. We understood what he meant because growing crops intensively requires a lot of soil preparation. Organic matter must be incorporated to maintain soil fertility, seedbeds must be prepared to encourage good germination, soil must be loosened and aerated to acclimatize young transplants, and crop residues have to be disposed of in time for the next seeding. All of this involves working the soil substantially.
Currently at Les Jardins de la Grelinette, our philosophy is to try and replace mechanical tillage with biological tillage. As we see it, earthworms play such an important role in healthy soil structure—their tunnels providing aeration and drainage while their excretions bind together soil crumbs—that we want to have them thrive in our gardens. We also believe that microbes, fungi, and other soil organisms, given that we do not compromise their action with soil inversion, can perform much of the tillage needed to create and maintain loose, fertile soil. As much as this sounds good, however, we still need to intervene mechanically to prepare seedbeds for crop planting and establishment. Finding the appropriate equipment and techniques to do so efficiently, without damaging the soil structure and the living organisms within it, has been a challenge for many years.
After several seasons of experimentation, we now use a method that is biological, practical, and appropriate for commercial growing. In the middle of the season, soil preparation on our permanent beds goes as follows:
• Green manures* and crop residues are shredded with a flail mower, then covered with a black tarp for two to three weeks. This smothers the previous crop and cleans out the weeds.
• We use a broadfork to deeply aerate the soil and encourage root development in the next vegetable crop.
• We spread the amendments over the bed and mix them in with a rotary harrow to a depth of 2 inches. The rotary harrow has a roller in the back that tamps down the soil and levels the bed.
• We do a final raking to remove any remaining debris and stones. The bed is now ready to receive the crop.
Not counting the tarp treatment, it takes about 30 minutes to prepare one 100-foot-long bed. For maximum efficiency in the preparation step, all the tools we use are standardized to a width of 30 inches and can do the job completely in a single pass. The elements of our system are described below in greater detail.
Raised beds form the foundation of our intensive cropping system. They provide the most space and labor-efficient layout for the market gardener and the most beneficial growing environment for the plants. The fact that they are permanent is key as it allows an optimal way of building and maintaining soil structure. After many years growing in such a system, I find it hard to even imagine growing vegetables any other way. Here is a list of the benefits of growing crops on permanent raised beds.
Given the right conditions, soil organisms can perform much of the tillage needed to create and maintain loose, fertile soil.
Better drainage. Raising the soil above ground allows excess rainfall to drain away from the crop zone and moisture to stay in the root zone, where it is most needed. In our northern wet climate, this practice is critical.
Soil warms faster come springtime. Since the beds are raised several inches off the ground, they intercept more of the sun’s rays during early spring. Faster drying and warming soil permits earlier seeding and transplanting. Plants will also grow faster once they are established.
No soil compaction. Beds are never walked on during the growing season, let alone compacted by heavy machinery. In this system, only the pathways get compacted by the grower’s footsteps. Avoiding compaction promotes loose soil structure, which in turn allows vegetable roots to extend deeply into the soil.
Higher yields. Unlike the typical single rows separated by pathways, plants in a raised bed system are uniformly spaced over the surface of a wide bed, allowing for a high plant density. In other words: increased yield per square foot of growing space.
Soil building. Using the same layout of beds and paths each year restricts organic amendments to where they are needed—the beds. Considering the large volume of amendments and compost required in an intensive system, it is the most economical approach to soil building.
Depending on the size of the garden, establishing permanent beds may take a few days or even weeks.
Leaving out the tractor. A permanent bed system saves the work of building new beds every year and is the most efficient way of farming without a tractor. Working and shaping large quantities of soil every year would otherwise require a tractor in order to work efficiently.
For all of the reasons mentioned above, I strongly encourage beginning growers to adopt permanent beds when organizing a market garden. But this being said, note that such a set way of doing things does require initial onsite preparation.
In 2011, we purchased a Berta rotary plow for our walking tractor. This tool takes the soil from under it and moves it to the side. It’s great for breaking new ground but even better for building raised beds.
Any major earthmoving project has to be dealt with first. Bumps and dips in the soil surface should be corrected, and if tile drainage is required, it will also need to be installed. When taking over a previously vacant site (e.g., a field or unused farmland), it might inevitably be necessary to use heavy machinery (plow, chisel, rototiller, etc.) in order to bring the land into a “workable” state. A tractor may also be needed to remove any large rocks from the site. When planning for this kind of work to be done, it might also be a good idea to establish an action plan for eliminating persistent perennial weeds such as quack grass, dandelion, and thistle. Repetitive tillage with large disks or harrows might help in that regard.
Once the groundwork is finished, then the real work begins. Depending on the size of the garden, setting up permanent beds may take a few days, or even a few weeks. Creating ours took a while since we had about 180 of them, each 100 feet long. The first thing we did was to mark off the perimeter of each plot (calculated to contain 16 beds of 48 inches center to center). We then used strings to indicate the width of each bed and dug the earth from the pathways onto the beds. It was a lot of work, but we were motivated by the fact that we would only be doing this once.
While laying out the beds, we also added large amounts of organic matter to improve the soil’s quality. In our case, the initial soil was already a desirable gravelly loam soil, and we incorporated about 7 wheelbarrows per 100 foot bed of a compost mix rich in peat moss. We also added lime to raise our pH, which at the time was on the acidic side. We’ve seen other market gardeners add sand to clay-based soils and clay to sandy soils. Along with adding compost, these amendments help improve a soil’s texture.
With regard to the height of the beds, I recommend mounding the soil about 8 inches. Over time the soil will settle, and after one or two growing seasons, the beds may be only 4 to 6 inches high. Raising the beds higher than 8 inches does not produce any significant advantages and only creates more work and higher costs. Many market gardeners seed their pathways with clover, but at our farm, we don’t follow this approach. We use the soil in our pathways to pile on top of beds that have already settled, and we also use the pathway soil to weigh down tarps and floating row cover.
A two-wheel tractor, which we invariably refer to as the walking tractor, is the ideal power source for the market garden. Versatile, robust, and easy to use, they are designed to do soil work on small cultivated areas. Although they are slowly becoming more known in North America, walking tractors are popular in Europe, especially in Italy where some of the better-quality ones are built.
Raised beds have a tendency to settle over time. For many years we hilled them with a plough hooked up to a small rototiller. Now we use a rotary plow fixed to our walking tractor. Every spring, we make sure to build up a few beds to ensure that they are all maintained every two to three years.
The handlebars of a two-wheel tractor can be turned sideways to allow you to walk without stepping on the newly prepared soil surface. Its light weight and small size make it an appropriate choice of machinery for cultivating in a permanent bed system.
We began working with such a machine after using the small garden-sized rototiller typically found at most hardware stores. While these rototillers can provide adequate tillage, there is a world of difference between them and the rugged walking tractor, whose gear shifting and locking wheel differential make it much more powerful and maneuverable. Like a 4-wheel farm tractor, they are designed to run many attachments with a single power source. Their PTO* can run all sorts of implements, such as snowblowers, generators, grass mowers, and even hay balers. Walking tractors are distributed by different companies whose experts are in the best position to offer advice regarding tractor and wheel size, horsepower, and other features. Recommended trade names and company addresses are provided in the tool appendix.
For us, the choice to use a two-wheel tractor in preference to a full-sized one was obvious from the outset. First, our site’s limited growing area discouraged us from wasting space for tractor turnarounds and headlands. A walking tractor, on the other hand, can pivot on the spot, thus allowing for better use of the available land space.
Second, we found that when shopping around for tillage equipment, the ones we favored were more readily available for the two-wheel tractor. Thirty-inch-wide implements are common for two-wheel tractors, but much less so for four-wheel tractors. Third, the price of a two-wheel tractor is much cheaper. A new one, including a flail mower and a rotary power harrow, cost us a fraction of the price of the compact tractor we were also considering. In the end, it was an easy choice that we never regretted making.
A two-wheel tractor usually comes equipped with a rear-tine tiller. As I mentioned earlier, this tool isn’t good for soil structure as it pulverizes and breaks up aggregates in the soil, making it more susceptible to compaction. Nevertheless it’s useful for mixing amendments and green manures into the soil and for preparing seedbeds when there is not time to cover the soil with a tarp or to manually remove crop residues. It is also helpful for really early springtime seedings when the soil is still cold. A quick pass with the tiller brings oxygen into the soil, warming it up for early production. At this time, earthworms and other soil creatures (who obviously don’t like to be pulverized by tilling) aren’t around, so it doesn’t bother us too much to invert the soil layers of a few particular beds.
In our garden, the equipment of choice for bed preparation is a rotary power harrow (often just called a power harrow). On this tool, multiple sets of tines rotate on a vertical axis, which till the soil horizontally. The result is that soil layers are not inverted and no vertical compression of the soil can lead to hardpan formation. It works the soil by stirring it instead of mixing it like a tiller does. Our power harrow is equipped with a steel mesh roller in the rear, which allows for incremental adjustment of the working depth of the tines. The roller also levels and pre-tamps the soil for good seed-to-soil contact. One pass with our power harrow gives us a perfectly conditioned bed for transplants and direct-seeded crops. Overall, it’s an amazing tool, and I would recommend trying it first before adopting any other tilling or spading device. The only downside is its heavy weight, making it more challenging to maneuver than a rear-tine tiller.
The rotary power harrow eliminates inversion of the different soil layers, which is useful in preventing dormant seeds from being worked up. Overall, it is a better bed preparation tool than a rotary tiller.
We also have a heavy-duty flail mower that shreds green manures and crop residues with astonishing ease. It was the acquisition of this equipment (also attached to our walking tractor) that allowed us to pursue working with green manures in the garden. Before that we only had a regular mower, which cut the stems at the bottom of the plant, leaving us with lengthy material to work with. When we then tried to incorporate that material in the ground, the green manure would get tangled around the teeth of our tiller, all too often jamming the machine. The flail mower, on the other hand, reduces mowed material to a very small size that is easy to incorporate—the mower’s many tines acting like knives to chop everything up. This was such a breakthrough in our market garden that I feel it is an absolutely necessary tool when thinking about growing green manures. The flail mower also makes it very easy to clean away old crops, a job we used to do by hand.
Although a rear-tine tiller is a practical device, its use ruins the soil structure every time. Pulverising the soil leaves it nice and fluffy for a short while, but by breaking up soil aggregates, the soil will eventually settle into a more compacted state. The weight and action of the tiller also causes a hardpan below where the tines reach, further decreasing soil drainage and the ability of roots to penetrate the soil.
Choose your implements wisely as this will directly influence your ability to work the soil properly. Before making any final decision about purchasing a two-wheel tractor, consider the implements you’ll be working with, as this might determine the brand, size, and engine horsepower. Not all walking tractors are equal. For example, some of them don’t have the ability to reverse the handlebars, which allows the tractor front or rear PTO capability. This feature is important because implements like the power harrow perform best in the rear (so that tire tracks are eliminated) while others like the flail mowers work best in the front. It might also be interesting to consider some of the smaller tractors available from Europe and Asia, as well as those being currently developed in the United States. Small electric cultivating tractors are not available yet, but they should be on the market within a matter of years. No matter which machine you choose, make sure that the implements you want are available and compatible.
The broadfork is a long U-shaped fork that loosens the soil about one foot deep without inverting or mixing it. Because of its ability to work the subsurface of the soil, this tool is an essential part of our growing system. It complements our other tools that are all intended for surface cultivation. The way the broadfork works is quite simple. The operator steps up on the crossbar, using full bodyweight to drive the tines into the ground, then steps backward while pulling backwards on the handles, causing the tines to lever upwards through the soil. A steady worker can broadfork a whole plot (16 beds, each 100 feet long) in about two hours’ time. Broadforks are also ergonomically designed to keep the user’s back straight, thus preventing the common aches and pains felt after a long day of manual work.
Other growers often argue with me that using a broadfork on a commercial scale isn’t efficient, but for the time being, I don’t see many realistic alternatives. The broadfork is a simple and economical solution that ensures well-aerated soil. As much as I think surface tillage is one of the answers in moving towards creating biologically intelligent growing systems, for many years I have observed the beneficial effects of deep tillage with a broadfork, and I strongly feel that the advantages of this tool are too important to let laziness dictate our practices. It is important to note that we use it only for crops whose roots benefit from deep tillage, and do not use it routinely before every single crop.
The broadfork is an essential and appropriate tool for the market garden given that it allows deep tillage of the soil while preserving the topsoil structure.
The broadfork traces its origins back to the grelinette, a tool invented in France by André Grelin in the 1960s. The tool we use on our farm is not the authentic French grelinette but rather a Canadian-made one modeled after it. We named our business, Les Jardins de la Grelinette, after the tool because it is so emblematic of our philosophy of efficient, environmentally sound, manual organic gardening.
Why worry about soil inversion? The delicate ecology of soil develops as it does for a reason. Bacteria, fungi, and earthworms, which all work to create soil structure, are found at a certain depth in the soil because it has the right moisture and aeration conditions. Turning your soil right upside down disrupts this ecology for at least a while, so that you cannot rely on natural forces to help do the job for you. Inverting the soil also brings up into the topsoil weed seeds that were dormant in the subsurface.
Tarps and Pre-Crop Ground Cover
One of the most important discoveries we made throughout the years has been that of relying on soil-covering tarps to smother crop debris when preparing new ground.
Until then, our only way of clearing the remains of finished crops and established weeds was to either till them into the ground with multiple passes of the rototiller or manually remove them. As we started to move away from relying on the tiller, we often favored handpicking out weeds and residues, rationalizing this time-consuming activity by telling ourselves that all this organic material we were bringing to the compost pile would eventually become great soil-building material. This way of working was labor-intensive and time-consuming, and our beds were never really cleaned of the smaller weeds.
I believe plastic tarps are just as beneficial to soil as other forms of mulching. We are often reminded of this when we pull back a tarp and are greeted by an abundance of earthworms.
Then one midsummer’s day, I bought a big black UV-treated polyethylene tarp to break open new ground where we planned to plant berries. My idea was to dry it out before putting it away in the shed. As it happened, it stayed there for 3 weeks, and when we finally moved it away, it struck us—the tarps had killed all crop residues and weeds, leaving us with a very clean bed surface to work on. We had stumbled onto a technique that was highly effective. Ever since, we have used tarps to cover the ground as a complement to our minimal tillage system.
Every time a harvest is done with, we immediately cover it. Depending on what crop is next in line on the schedule, the tarp will remain on the bed for anywhere between two to four weeks, leaving our minds worry-free. Passively, we are preparing the soil for the next seeding while also weeding it just like false seedbed would.
Over time we have consistently noticed a difference in weed pressure on beds that have been covered compared with others that have not. The explanation is simple: the tarp creates warm, moist conditions in which weed seeds germinate, but the young weeds are then killed by the absence of light. Looking into this, we found out that French growers were widely using this technique (called occultation) to diminish, or even eliminate, weed infestations in their fields.
The relationship between soil health and tillage is a hot topic for debate among practitioners and researchers in the organic farming world. It’s generally understood that plowing, disking, and harrowing, although so practical for soil preparation, also have their downside. Working the soil makes it more prone to erosion, disintegrates its structure, and damages living organisms. Tillage also takes time, and remains the major use of fossil fuels on organic farms. Even some conventional agricultural scientists now claim that soil fauna and flora are too easily affected by soil disturbance, concluding that tillage should be avoided. For them, however, no-till is associated with increased chemical herbicide use, such as glyphosate in seedbed preparation. For me, replacing tillage by the use of Roundup is not something I can vouch for.
Covering the soil with an opaque tarp for a few weeks is how we manage to clean the surface of our beds without having to work the soil. This technique is also quite beneficial in reducing weed pressure for the following crop.
The concept of no-till has been around for a long time, and many books, articles, and websites assert the benefits of not disturbing soil integrity when growing crops. The general thrust behind the concept of no-till is that amendments and crop residues are better-off left on the soil’s surface than incorporated by tillage. Mulched organic matter is eventually incorporated by the action of worms, fungi, and microbes that thrive in undisturbed soil. This practice mimics the actions of forest floors, which do not require tillage and can sustain themselves for centuries, if not longer.
While in general this is a great concept, in the market garden, no-till is restrictive and somewhat impractical. Based on my experience, direct seeding into crop residues, mulch, or crimpled down cover crops is not straightforward, causing unpredictable germination rates—a nightmare for any commercial grower. Also, shallow cultivation of the soil is the best way I know to keep weeds in check and prepare seedbeds. Moreover, I have never come across direct evidence that tilling the soil results in lower yields. All the best commercial growers I know heavily till the land and still obtain great results in terms of their quality of production and soil sustainability.
In 2007, Eliot Coleman and his team developed a small cultivator that is operated using a battery-powered drill. The cultivator makes it possible to mix in compost and refine the soil in the top few inches. Although it is often not powerful enough to be used on the whole garden, it can be a useful tool in greenhouses, where a walking tractor doesn’t maneuver easily.
For us, at this point in time, we find that a middle ground is the best approach. Our current minimum tillage methods give us satisfying results when it comes to increasing yield and saving time and effort. I feel we have struck a balance between theory and practice, yet I am convinced that this is only the beginning: by keeping up to date with new ideas and strategies, I am confident that we will develop better ways to further harness the biological power of the soil, instead of relying on mechanical solutions. Relying on and working in harmony with ecological systems is the wave of the future.
In conclusion, I feel it is important to stress this final point: while many aspiring organic growers gravitate towards ideas associated with permaculture, sustainability, and alternative energy, it’s also important to understand that market gardening is a livelihood before anything else. Although experimenting with novel ways of doing things is exciting, I would not be too hasty in brushing aside proven solutions from experienced growers, even if they do not seem “ideal.” When first starting out, the important thing is to be successful at growing vegetables. If the idea of minimal tillage or no-till inspires you, keep in mind that it is an approach, not a doctrine.
* If the green manure is thick, we sometimes partly turn it under with a quick pass of the power harrow or rototiller (to a depth of three to five inches) before covering it with a black tarp.
* PTO stands for Power Take Off. This is the part where the engine of a tractor powers the implement via a rotating shaft.
