Blog

To recap P. 1, building healthy soil in the garden means taking care of the billions of living organisms underfoot. It’s not as big of a job as it sounds. In our small community garden plots, we can adjust our practices easily and work less by retiring old methods like double-digging and other strenuous soil churning. Easing up on soil disruption protects its complex ecosystem and makes for happier plants.

Soil for the Planet

If that’s not enough to convince you to put down the shovel, consider the climate. One of the key drivers of climate change is the burning of fossil fuels, but did you know that some modern agricultural practices–including tilling–also have released significant amounts of carbon into the atmosphere?

Where is that carbon coming from? It’s right there in the soil, everywhere.  It’s in the roots of plants, in decaying leaf mulch, in earthworms, in sugars released by plants, and in long threads of fungal networks. Around 50%  to 58% of the organic matter in soil is carbon.

Unfortunately, our cultivated land has lost around half of its organic matter, from 5% levels of soil organic matter down to less than 3%. We want that carbon back! Soil life is built from carbon and depends on it to survive, which makes soil a great reservoir for carbon. In the soil it can do good things for us, whereas too much of it in the atmosphere contributes to climate change.

Regenerative agriculture or carbon farming aims to do just that–to put carbon back into the soil using a variety of practices, including no-till farming. It’s not a straightforward process. Some of the systems at work in the garden naturally put carbon back into the atmosphere no matter how carefully we tend our soil. For example, all of those wonderful soil microbes expire carbon dioxide when they break down organic material. Microbes in an acre of corn can expire as much carbon dioxide as twenty five active men.

In very rough terms, it’s a two-step-forward/one-step-back kind of a process, which means that the goal of carbon farming is to put more carbon into the soil than is released. Here’s where things get a little tricky and controversial, figuring out the best agricultural practices to sink the most carbon and keep it in the soil. Soil scientists have paid attention to a substance called glomalin, produced by fungi, which acts like a glue holding soil particles together in aggregates. (Remember, that cottage-cheesy, pebbled texture?) Some scientists think glomalin may tie up 27% of soil carbon for as long as 40 years.

Soil scientists have also paid attention to humus, the carbon-rich, coffee-colored, fertile part of soil. It’s hard to define humus exactly because it’s not clear how humus is formed; some think it’s a product of decomposition of organic matter, while others think that it’s a built-up product of soil organisms utilizing the sugars exuded by plants. In any case, the important quality of humus is that like glomalin, it’s considered by many to be recalcitrant, meaning that it’s likely to stay in the soil for a long time. These are the kinds of long-term storage we need to draw down the imbalance of carbon in the atmosphere.

Farmers worldwide are already using regenerative agricultural practices, in no small part because they improve productivity and in the long-run, make economical sense. Green America is cheering on home gardeners to do the same.  Their idea is this: our individual plots may be small, but collectively, we might be able to make a difference, similar to the way victory gardeners of WWI and WWII grew up to 40% of the fresh produce consumed in the U.S..

This slideshow requires JavaScript.

The posters above were published by the U.S. Food Administration, created by Woodrow Wilson by executive order in 1917. Leading the newly-formed administration, Herbert Hoover had the power to act as “food dictator,” but strove to design “an effort that would appeal to the American sense of volunteerism and avoid coercion.” (I know I’m getting a little off track here, but I think this is interesting stuff and definitely relevant to the question of how to get large groups of people to act quickly in helpful ways for a common cause–like climate change.)

Bottom Line?

Ditching some of our old gardening methods may not only build the soil for our plants, but also may make a positive impact on the planet. I’m convinced at the very least that  strategies that support soil life yield more productive, sustainable, and healthier gardens. As we’ve said before at PPCG, our only organic gardening rule that we enforce is  “no synthetic agricultural chemicals.” But I hope you’ll consider making some changes in how you tend your plot, if for no other reason than you’ll get better results. For more info, take a look at the links below.

Up next, since I know we’re all itching to get in the garden: regenerative techniques we can use in our own gardens.

---

For More Info…

For starters, a nice graphic comparing “regenerated soil” vs. “dead dirt,” from Green America.

Here’s another good place to start. This short video explains regenerative agriculture in easy-to-understand language, from Kiss the Ground. And here’s a scripted version with some added details.

Another accessible piece–on fungi and their role in the carbon cycle–from NPR.

From Green America, understanding the complexities of soil.

From Northeast Farming Association (NOFA), really helpful white paper on soil carbon restoration. Read this if you want to go into more depth on this topic. It’s written for the general public and covers a lot of ground.  NOFAMass has become my favorite go-to source on soil-building.

From the New York Times Magazine, an article on changing agricultural practices to draw down carbon from the atmosphere. (Local readers: if you don’t have a NYT subscription and have used up your free monthly articles, our local library offers free three-day passes. Here’s a link to digital media.)

The Soil Will Save Us by Kristin Ohlson (2014). I haven’t been able to get a copy of this book yet, but it looks like it’s available through Boston Public Library.

From nature.com, a relatively short, but more technical presentation of soil carbon sequestration. This was the first piece I read that helped me understand the balance of carbon inputs and outputs. Also covers some aspects of carbon sequestration such as soil mineralogy and land topography.

SOS: Save Our Soils. Very interesting 2015 interview with Dr. Christine Jones, soil ecologist. Some of this material was not fully explained for the general reader, but it covers a broad range of topics.

Want more posters? (I love this stuff!) Google ‘victory garden posters’ and ‘women’s land army.’

 

Let’s talk about soil. I made this pitch last spring and since then, I’ve learned more about soil and noticed a lot of interest in it in popular media. (See links below.) So I’m recharging my appeal this year: before we get into our gardens this spring with shovels, stop and consider the soil in your plot and how to protect and make good use of it.

Organic

A simple rule in our organic community garden is that we don’t use any agricultural chemicals. This one’s easy. We all know that products such as Roundup and Sevin aren’t healthy for us or the environment in many ways.

But organic gardening is more fundamentally about supporting nature and working with it. With regard to our soil, even the act of digging into it can mess up its natural beneficial processes. In some ways, less is more. Stop disrupting your soil, and it will thrive and work better for you.

Home Soil

Last fall when I dug a shallow trench to plant my garlic, I felt bad about displacing a handful of earthworms. Those critters were just the obvious living organisms in my garden. A teaspoon of good quality soil is populated with more microorganisms than people on earth. That’s billions of algae, fungi, bacteria, yeasts, protozoa, nematodes, and more. Scientists are only beginning to understand the complex ecosystems in soil and how they support plant life.

Here’s a simplified description of the relationship between your plants and microbes:

• Plants take in carbon dioxide and through photosynthesis, use the carbon atoms to form sugars.
• Some sugars are released into the soil through the plants’ roots, providing food for microbes.
• These microbes, in turn, provide important nutrients right to the root zone of the plant.
  

Microbes act like home delivery food service. Sounds good, right? Here’s another point to understand: good soil with organic matter holds together in small clumps (aggregates) separated by open pores. Microbes thrive in this kind of environment; in fact, they depend on good soil structure for critical functions. Taking a shovel to it is like bulldozing their natural habitat. And destroying their home means your plants are going to be deprived of the little guys that nurture them. Your plants themselves like good soil structure for other reasons, too.

Soil Care

How can you tell if your soil has good aggregation? A handful of well-aggregated soil has the pebbled texture of cottage cheese. Soil that is poorly aggregated, in contrast, doesn’t hold together at all, or if you gently squeeze it, forms into larger chunks that don’t crumble nicely into pea-sized pieces.

Other bad consequences come from churning up your soil. For example, “tilling soil causes pore spaces to collapse and seal over, causing more rain to run off than sink in.” Your plants aren’t getting that water and worse, water run-off carries away your garden soil. Tilled soil is also lower in organic matter.

I like this description, relayed by Sharon Gensler, the Soil Carbon Outreach Coordinator at NOFA/Mass. “Poor soil is like a mound of flour, which sheds water poured on top rather than absorbing it. On the other hand, water poured over a stack of sliced bread is easily and quickly absorbed. The bread has crumb and texture, with many pours available to absorb and retain the moisture, while the flour is dense with very little porous space for absorption of air or water.”

Last summer, I took over a plot that another gardener couldn’t use. The plot had grown

“weedy”  with purslane (an edible plant, though not my favorite), so I set about clearing the entire plot. My thinking went like this: I’d clear the purslane so it wouldn’t compete with my garden plants for water and nutrients, and then I would cover any bare areas with compost and mulch to protect and build the soil.

Once all of those plants were cleared, however, I found I was left with dry, dusty soil that didn’t hold water well. Have you ever had a problem with hydrophobic soil? You might have experienced it when you let a flower pot filled with a peat-based mix dry out. No matter how much I watered the cleared garden, the soil seemed to repel, rather than absorb the water.

I went ahead as planned and covered the soil with compost and wood mulch–which helped with the watering problem, eventually–but I would not have had to remediate so extensively if I had selectively left some of that purslane in place. In many cases, a living root is better than compost and mulch. To be clear, I’m not advocating for letting any weed run rampant in the garden; certainly some weeds will outcompete garden plants. But in this case, I should have thought of that purslane itself as a garden plant–not only because it was edible, but also because it would have been a good friend to my garden, protecting the soil from erosion, supporting microbial life, and helping to retain water.

Bottom Line?

Start with soil! Make friends with the billions of organisms living underfoot, and they’ll do a lot of heavy lifting for you and your plants. Setting the shovel aside is just one way to keep your soil zoo happy. I’ll talk about what I’ve learned about no-dig and other soil-building methods, but up next in Part 2: Good Soil for a Healthy Planet.

---

For More Info…

From Green America, understanding the complexities of soil.

Interesting fact sheet from the USDA on soil health.

The Zoo Beneath Our Feet, from the Washington Post.

What is humus? From National Geographic.

Got worms? Earthworms can be an indicator of soil health. From MSU Extension.

How to Turn Dirt Into Soil From Yes! magazine, home gardeners share their experiences.

A deeper dive into soil aggregation. From the Soil System Sciences (SSS) Division of the European Geosciences Union(EGU).