Benefits and Detriments of “No-Dig” / “No-Till” Methods

“No-dig” or “no-till” methods date back centuries but have been increasing in popularity in recent years due to their simplicity and effectiveness. In fact, “no-dig” or “no-till” beds have so many benefits that it makes sense why they’re becoming a favorite of gardeners everywhere. While it’s true they don’t yield the same health and production as some other top-notch methods, like double-digging and spading, for especially deeply-rooted crops, they are much easier and work well enough, and just as well for lettuce, spinach, and others, that most gardeners will be thrilled with their plants’ health and production. Like any method, they have their possible detriments, but most of these stem from one particular site preparation technique and are easily solvable. All in all, “no-dig”/”no-till” methods provide gardeners with an incredible additional tool in their toolbox, especially one that allows them to start growing in an area even while smothering the existing vegetation.

Benefits

Fast and easy. Possibly the biggest benefit is that is one of the fastest and easiest bed preparation methods, making gardening more accessible to a wider range of people, especially those who don’t want to or aren’t able to partake in some of the more time-consuming or strenuous methods.

Doesn’t disturb the structure of the soil or soil life. Soil naturally develops structure—a combination of cracks, holes, and clumps of soil aggregates that create pore space. Healthy soil is 50% pore space filled equally with the air and water plants’ roots need to thrive. Healthy garden soil is also absolutely filled with soil life. Earthworms tunnel and eat organic matter, leaving nutrient-rich castings, in their wake. Stag beetles, sow bugs, spiders, and many other arthropods form an intricate food web. Tiny microbes break down organic matter and slowly release the perfect kinds and proportions of nutrients for your plants. And fungi transport minerals to plants in exchange for carbohydrates through a densely filigreed network. Tilling breaks up much of the soil structure and disturbs or kills at least some of this soil life. With the possible exception of burying some aerobic microbes too deeply, a “no-till” approach keeps all of these completely intact.

Doesn’t bring new weed seeds to the surface. Since many weed seeds stay viable in a dormant state in lower levels of the soil for years or even decades, most garden soil is filled with an almost incalculable number of weed seeds. Freeze-thaw cycles, erosion, tilling, and other cultivation are the mechanisms that bring new batches of weed seeds to the surface, where they’re finally triggered to germinate by the changes in temperature, moisture, oxygen, and/or light that break dormancy and signal they’ve finally found a suitable place to grow. One great advantage of a “no-till” or “no-dig” approach is that it avoids bringing weed seeds to the surface through tiling and other forms of cultivation. Plus, each method specifies adding additional material on top of the soil—cured compost, mulch, piles of composting materials, or straw bales—further burying weed seeds, and continually adding to this depth each year—with more cured compost, mulch, or new straw—wise practices no matter the method used.

Adds crucial organic matter to the soil. Ideal garden soil is about five percent organic matter, which is largely responsible for the health of our soil and contributes the macro-and micro-nutrients our plants need for healthy and productive growth. Most of us, however, have soils that are far below this ideal. All “no-dig/no-till” methods add organic matter to the soil, and some of them, namely adding 6″ of compost and lasagna gardening, add about the maximum amount one should add initially, and then annually add just the right amount to get our soil back to that ideal five percent. Even if I were still gardening in several feet of rich, black, hummus-filled, midwestern loess and prairie soils—to which adding six inches of compost on top seems like dropping a swimming pool’s worth of water on a Lake Superior—I’d still be adding organic matter just to constantly replenish what my garden plants are using. It’s good to give back.

Allows a gardener to use the garden space of a prospective bed while the vegetation underneath is being smothered. If you’re smothering existing vegetation or sod during the growing season, you can use a preparation technique for these methods that allows you to grow vegetables in that spot at the same time (See “Option 2” in “Clearing Existing Vegetation for ‘No-Dig’/’No-Till’ Beds”). It has some significant downsides, discussed below, but even otherwise deeply-rooted garden plants do surprisingly well growing in 6″ of added compost or lasagna methods used on top of this preparation technique.

Most plants grow well. While you might not get the massive growth in tomatoes, peppers, and larger brassicas (broccoli, cauliflower, and cabbage) that you do from methods like double digging, many garden plants do quite well in this method. And with plants like lettuce and spinach, you might not notice any difference at all.

Possible Detriments

Before you build a “no-dig/till” bed, it’s best to rid the area of its existing vegetation, so it doesn’t grow through your “no-dig/till” bed’s materials and become a weedy headache. One technique for doing this is to smother the vegetation under an eight-to-ten-sheet layer of wetted newspapers laid down before the material of the “no-dig”/”no-till” bed—the cured compost, layers of composting material, mulch, or straw—is added. The first three of these detriments apply only to this preparation technique.

Not enough space for roots. Most garden plants have extremely large root systems, many reaching four feet or more deep and several feet wide. If you choose to smother the existing vegetation with a layer of newspapers or cardboard, the relatively impenetrable nature of the layers of newspaper or cardboard that allows it to smother the existing vegetation also makes it more or less impenetrable by roots and shoots for the first few months of your growing season. Since it takes months to break down to a more penetrable state—which is why it works so well to smother the existing vegetation—this gives your plants only the relatively thin six inches of added cured compost in which to grow for most, if not all, of that first gardening season, keeping your plants from rooting as deeply as they otherwise would, significantly limiting their ultimate potential for maximum health and production. Looking at the pictures below, it’s clear that six inches is nowhere near enough depth to accommodate the full potential of your plants’ roots.

Doesn’t loosen deeper soil. Traditional “no-till”/”no-dig” methods don’t loosen the underlying soil at all. Loosened soil, however, makes it much easier for these plants’ extensive networks of roots to grow to the maximum depths and breadths they naturally reach to find the necessary water and nutrients they need to fuel their maximum size, health, and production, and the deeper the better.

Still, while many plants—especially the deeper rooted ones like tomatoes, peppers, and the larger brassicas—may not do as well in “no dig” methods as they do in methods that loosen the soil deeply (e.g. double digging, spading/forking, or to some degree mounding tilled ground), many garden plants, especially shallower rooted ones like lettuce, do just as well due to the dual facts that they aren’t that deeply rooted at the point in their growth cycle that they’re harvested and they’re literally growing in six inches of loosened pure cured compost and so have all of the nutrition they need.

Doesn’t aerate deeper soil. This method provides one of the key ingredients to soil and plant health: organic matter. However, it does little to provide for the other—aeration—and even works against it a bit. While the added organic matter will be plenty aerated since it was loosened naturally as it was added, placing compost directly on top of the existing soil does nothing to aerate the deeper soil. If anything, it decreases the amount of air getting to it and flowing through it. Since available organic matter (as a source of food) and the air provided by airflow through pores in the soil and added during mechanical aeration (as a source of oxygen and other key elements)are the keys to microbial growth, and microbial growth in the soil is the key to ultimate soil and plant health, this is a key detriment of the classic “no-dig”/”no-till” method. However, if gardeners aren’t dogmatic in their “no-dig”/”no-till” approach and, instead, loosen the soil the first year (with a digging fork, spade, broadfork, or even a method like double-digging), they get all of the benefits of aerating their soil deeply while maintaining the ease and other benefits of the “no-dig”/”no-till” approach for the future.

Doesn’t add cured compost to deeper soil. The ultimate goal of a gardener is to provide the ideal conditions for the entirety of their plants. Adding plenty of aeration and cured compost deeper into the soil creates the ideal conditions of excellent fertility and increased ease of growth throughout much more of your plants’ growing area.

Tends to compact the soil if use newspaper layer. What’s more the soil underneath newspapers or cardboard ends up quite compact. We first noticed this when feeling the digging fork jar our hands and stop abruptly with each thrust while harvesting potatoes from a “no dig” bed at the end of the first year. Curious, we dug down and were surprised to see most of the wetted newspapers intact, some even readable. Wondering how it would fare over time, we left the “no dig” beds alone, except for adding more cure compost to the top, to be tested again at the end of the next season. At the end of the second year, the soil was still significantly compacted under the compost, leaving probing thrusts with the digging fork jarring our hands as it stopped at a seemingly impenetrable layer. Even more curious, I dug into the layers of every bed and found a hardpan had developed right under the cured compost in each bed. The soil we started with underneath each bed had been amended regularly each year beforehand, had soil-loosening cover crops on it each off-season (including the one just before), and was pretty spongy when we put down the six inches of cured compost. None of it was anywhere near as compact as it was even three years after the compost had been laid on top of it. It was as if the newspaper layer acted as a big snowshoe holding all of the weight of the compost above and compacting everything underneath it enough that it still hadn’t recovered by the end of the second year.

Dries out quickly. Cured compost dries out quickly. Plus, if a layer of newspapers or cardboard is used to smother the existing vegetation, the compost is cut off from the wicking action of water upwards from the water table. Both of these lead to gardeners having to water more often.

Can lead to weed problems. If one doesn’t use newspapers or cardboard to smother the existing vegetation (and even if one does), persistent perennial weeds will easily grow through the six inches of compost and become a problem. Without digging, it’s really hard to unearth all of their root systems.

Is that much compost sustainable? Is adding six inches of compost to every garden bed and then another two inches to each one every year sustainable? If everyone were to do this, is there even that much compost being made? I don’t know, but while there are relatively few of us looking to add it to our soil and it’s relatively inexpensive and easy to get or make, add as much of it as possible to get your soil back to five percent organic matter.