Regenerative agriculture works to restore the health of our planet’s soil, but here is an important question: What does restoring soil health actually mean?
Many who are new to regenerative –– even if they support the goal of healthy soil –– don’t know what’s wrong with the way soil is now or what needs restoring. In honor of World Soil Day on December 2nd, here is our introductory overview.
When regenerative farmers or ranchers talk about restoring soil health, they are usually focused on three specific attributes. Let’s examine those now, and then we will explore some of the techniques used to address them.
Soil Health Sign #1: Carbon Sequestration
As we discussed in our article Regenerative Ag: A Tool to Fight Climate Change, soil contains significant amounts of carbon dioxide –– the greenhouse gas that is the main culprit of climate change. When soil is tilled or plowed in the course of “normal” (non-regenerative) farming, it is disturbed, and some of the carbon is released into our atmosphere. This is not only bad for the environment, but also for the soil, which requires carbon for optimal water-retention and fertility. Plants absorb more nutrients from carbon-rich soil than from soil with less carbon.
According to Ohio State University’s Carbon Management & Sequestration Center, “the world’s cultivated soils have lost between 50 and 70 percent of their original carbon stock.” For this reason, carbon sequestration –– the amount of carbon that can be made to stay in the soil –– is a key objective for all practitioners of regenerative agriculture.
Soil Health Sign #2: Erosion
Soil is constantly being eroded –– by wind, by rain, and most certainly, by farming. Yet, while some amount of erosion is natural and it can never be completely eliminated, many of our farms are nearing a dangerous threshold.
When soil erodes too much, it becomes less able to store the water and nutrients that plants need to grow. Erosion also exposes the subsoil (made up mostly of weathered clay and rocks) because the topsoil (which contains most of the nutrients and minerals) has been destroyed or diminished.
Past a certain point, eroded soil is no longer viable and cannot support plant life at all. It’s a serious issue: a scientific paper in Nature Communications states “that 75 billion tonnes (Pg) of soil are eroded every year from arable lands worldwide.” The way land is managed has a big impact on its rate of soil erosion, which is a major focus of the regenerative agriculture techniques we’ll explain shortly.
Soil Health Sign #3: Biodiversity
Strong and fertile soil is, above all else, biodiverse. Nutrients like nitrogen, phosphorus, and potassium, sulfur, calcium, magnesium are present in an optimal balance. The soil has adequate amounts of water. Heavy metals and acidity (which deter plant growth) are at a minimum. As the UN’s Food & Agriculture Organization (FAO) puts it:
“A typical, healthy soil might contain several species of vertebrate animals, several species of earthworms, 20-30 species of mites, 50-100 species of insects, tens of species of nematodes, hundreds of species of fungi and perhaps thousands of species of bacteria and actinomycetes.”
Plants grown in biodiverse soil conditions absorb more nutrients and have more nutritional value for humans. Unfortunately, when soil is tilled using normal farming methods, it loses these properties and becomes less biodiverse over time. As with carbon sequestration and soil erosion, however, certain methods can improve the biodiversity of soil managed in a regenerative manner.
Each of these deserves (and will get) a full post in the future, but for now, here are three of the main regenerative methods that demonstrably help restore soil health.
Cover cropping is when plants are planted to cover the soil instead of for harvesting. When done properly, cover cropping reduces soil erosion, improves soil fertility, and promotes biodiversity. A common example of a cover crop is winter rye, which is often planted in the fall or early winter. This plant has a deep root system, is drought-resistant, and also helps to loosen compacted soil.
When planted in parallel with a legume (such as clover) this ensures that there will be more nitrogen in the soil when the next season’s crop is grown. This is just one example of cover cropping –– the technique has many applications, and can even help farmers increase their incomes in addition to the environmental benefits.
Crop rotation is when farmers grow a series of different crops in one area over several growing seasons. (Instead of growing the same crop in the same place indefinitely.) This reduces the reliance on one set of soil nutrients, and the likelihood of resistant pests and weeds.
Which crops to rotate, when, and in what order depend on many variables that are specific to the land in question. How a given crop contributes to the soil organic matter (SOM) content, that crop’s ability to manage deficient or excess nutrients, whether it causes (or reduces) soil erosion –– these are just a few of the factors that regenerative farmers consider when designing a crop rotation strategy.
Let’s say, to give an example, that a farmer has just finished harvesting a field of corn. He might then decide to plant beans there, because of the fact that corn consumes a great deal of nitrogen from the soil, and beans return nitrogen to it. A simple rotation might involve two or three crops. Complex ones might incorporate a dozen or more.
Rotational grazing, meanwhile, involves moving livestock to different portions of pasture while the pasture they were just on gets to rest. This allows the pasture as a whole to better-resist soil erosion. Which, in turn, sequesters more carbon.
There are several rotational grazing systems that each suit different kinds of farms or ranches.
- One is strip grazing, where electric fences are put in place to give animals enough pasture to grain for a few hours or days.
- Another is forward grazing, where two groups of animals from the same species graze one piece of pasture. Typically, younger animals graze the top of the plants (where the most nutritious leaves are) and the second group forages what is left behind.
- Mixed grazing is when different kinds of livestock (cattle, sheep, horses, goats, etc.) graze at the same time on the same pasture.
There is much more detail to how regenerative agriculture restores soil health than we can cover here, but now you know the fundamentals!