Welcome to Book of the Week – offering you a glimpse between the pages! Get the Book of the Week email newsletter delivered directly to your in box! This week’s Book of the Week feature, produced by Chelsea Green Publishing, is The Living Soil Handbook, by Jesse Frost. The following excerpt is reprinted with permission from the publisher.
Let’s consider the impact of tillage on the key factors needed for photosynthesis. A good place to start is to simply define the word tillage.
Many dictionaries describe tillage as “preparing the ground to grow crops.” For centuries, that’s all it was. Dating back to the earliest agrarians, Indigenous farmers prepared small plots of ground by hand or with animals, using implements made of stone, bone, wood, and later, metals. Certainly, many of these traditional practices opened up and exposed the soil temporarily. The scale of farms was generally small. Fields were regularly fallowed — that is, they were encouraged to go back to hosting wild plants — several years at a time, which replenished nutrients and repaired soil structure. These practices served farmers for thousands of years, and many indigenous cultures still practice these small-scale growing methods.
Over time, though, the scale of farming changed, and with it, the definition of tillage shifted. The development of new tools enabled farmers to open up and plant larger and larger plots of land. Cast-iron implements replaced wood implements, and then steel replaced cast iron. Powerful tractors entered the picture, followed closely by chemical fertilizers. Changing practices in farming led to huge swaths of exposed soil, and an increasing potential for soil degradation. Unfortunately, that potential has been realized many times over.
To understand how large-scale mechanical tillage begets soil loss, think of soil as a major underground city. Like all cities, soil requires infrastructure. It needs tunnels for the transport of air and nutrients, and it needs housing for its residents (soil organisms). It needs a stable physical structure that allows water to flow laterally and to drain vertically. In living soil, plant roots and soil aggregates bind the soil together, creating vital stability. Earthworms carve tunnels, making it easier for air to come in, carbon dioxide to leave, and fungal hyphae and plant roots to thread their way through. However, when we crush that infrastructure by tilling and poison that soil life by applying pesticides or chemical fertilizers, we render the soil vulnerable to erosion.
Soil organic matter is plundered in major tillage events. Soil aggregates are broken apart and oxygen is simultaneously whipped into the rhizosphere. Newly enlivened oxygen-loving bacteria begin to feast on soil organic matter and respire it as carbon dioxide. Because there are few or no plants present to capture much of that carbon dioxide gas and return it to the carbon cycle, it flows into the atmosphere unobstructed.
Mechanical tillage is catastrophic to fungal populations. Bacteria are highly adaptable to changing conditions, but many fungi require significant time and energy to build a mycelial network. Mechanically churning the soil rips all of that apart and the fungi must begin again, starting from the level of individual spores. Nematodes, arthropods, earthworms, and other predatory organisms likewise get pummeled when organic matter is lost by being tossed onto the soil surface where it burns up in the sun, blows away, or is swept off by heavy rain. The end result is a soil rich with bacteria, low in predators, and with damaged fungal populations. This type of soil primarily favors the growth of plants that a soil ecologist might praise as adaptable, but that farmers would condemn as unwanted weeds.
The ecological risks that accompany regular plowing and mechanical tillage don’t stop at microbial devastation, organic matter loss, and erosion. If the soil is worked when it’s too wet, tillers, plows, and other similar implements can create various types of compaction in the soil. These types of compaction are a significant barrier to creating healthy soil, and they limit crop production and soil health tremendously. Surface compaction occurs when bare soil is exposed to heavy rains or foot traffic. This form of compaction inhibits water penetration and limits respiration. Hardpans are compacted layers that generally form at the greatest depth a farm implement reaches, and these deep hardpans can inhibit root and water penetration. This type of compaction is stubborn and can persist for many years even after a farmer adopts good soil management practices.
Many bacteria and some fungi can survive in compacted soils, but microbial predators such as nematodes often suffer. Without those predators, bacterial populations increase but nutrient availability may not. Moreover, if water cannot properly drain, photosynthesis slows or stops entirely while microbes and plant roots drown. The microbes that survive such saturated environments begin to consume the available nitrogen, leading to nitrogen loss (denitrification). Both carbon dioxide and hydrogen sulfide gasses may build up and become toxic to plant roots.
With these negative impacts of tillage in mind, let’s explore the idea of expanding our concept of tillage. Tillage is not solely the outcome of using a tiller or disc or plow. Many other kinds of tools can cause some or all of the problems we generally attribute to mechanical tillage. It is not the tool but the user who determines whether a particular act of tillage creates minor soil disturbance or major soil disturbance. Put another way, it is not the tool that decides how to till a piece of land, how long and how intensively, and how to follow up after tilling — those are the decisions that farmers make, and that determine long-term soil health and performance.
To underline this point, let’s compare and contrast some tillage tools and how they can be harmful or helpful to the soil depending on how they’re used. First on the list: the rotary tiller. When used as the primary means of soil preparation year after year, this tool can absolutely devastate soil ecology and structure, repeatedly encouraging all the aforementioned issues. That said, in some cases, a tiller may be ideal for starting a garden. When a farmer or gardener uses a tiller appropriately, this tool can break up existing compaction layers and inject composts and amendments into depleted soils, rapidly preparing them for production, and thus improve that soil’s potential to support photosynthesis.
Consider another — sometimes controversial — tool in the no-till world: the broad fork. This large fork has long tines and farmers use it to gently decompact soil. The farmer stands on the crossbar to force the tines into the soil, then steps off and pulls back on the handles, lightly lifting the tines enough to simply crack the soil surface. However, the broad fork can easily be used to heave up large chunks of soil and flip them over, breaking the soil apart and damaging fungal populations, exposing carbon stores, and injecting large amounts of oxygen into the soil thus encouraging an organic matter feast by bacteria.
A less obvious tillage tool is the silage tarp, which is popular for covering an area of prepared soil to cause weed seeds to germinate and then die, or over a crimped cover crop to help terminate the cover crop. But when left in place too long, a silage tarp can also be a form of tillage. Tarps are heavy and can create surface compaction. Exposure to UV radiation causes the tarp fabric to break down and shed microplastic particles, which can be harmful to soil life. Polyethylene tarps do not allow for much gas exchange, potentially creating an anaerobic environment that may encourage pathogenic microbes. This practice may not look like classic tillage—it does not invert or blend soil layers—but it has some of the same negative effects that we associate with tillage systems.
All that to say, when we’re working toward a no-till, living soil system we need a clear definition of what we’re trying to avoid. We also need a more comprehensive representation of what constitutes tillage. In the English language, words can flip meanings from one generation to the next. Awesome used to mean something that evoked terror. Egregious used to mean distinguished. The meaning of tillage has flipped, as well. Tillage no longer simply means preparing ground for growing crops. Increasingly, tillage is a set of practices that make the soil less capable of growing anything at all. I suggest that we call tillage what it is: anything done to the soil that does not ultimately promote soil health.
About the Author:
Jesse Frost, aka Farmer Jesse, is a certified organic market gardener, freelance journalist, and the host of The No-Till Market Garden Podcast. He is also a cofounder of notillgrowers.com, where he helps collect the best and latest no-till insights from growers in the United States, Canada, the UK, and Europe. He and his wife, Hannah Crabtree, practice no-till farming at Rough Draft Farmstead in central Kentucky.
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