Tuesday, October 20, 2015

Backyard Carbon Sequestration: What Does Synthetic Fertilizer Have to Do with It?

Part two of a series exploring how regenerative gardening techniques can enhance carbon storage while improving soil health. In part one I discussed some of the principles behind the factors involved in soil health and how plants and the soil biological community work together to store carbon and build appropriate fertility. “Why Not Start Today: Backyard Carbon Sequestration Is Something Nearly Everyone Can Do” can be found here. 

 A brief digression about the term “regenerative gardening” 
So what is regenerative gardening, anyway? Regenerative gardening is an umbrella term that embraces many styles and traditions of organic cultivation and adds explicit intentionality regarding carbon sequestration. The recent Rodale white paper, “Regenerative Organic Agriculture and Climate Change,” says that, “regenerative organic agriculture refers to working with nature to utilize photosynthesis and healthy soil microbiology to draw down greenhouse gases.” The same goes for gardening. Like regenerative farming and ranching, regenerative gardening aims for land cultivation and management that builds soil health and helps improve the health of the ecosystem within which that garden is located, while growing plants and harvesting crops useful to humans, whether food, medicine, fiber or wood—and along the way, creating beauty. And, doing all this while, importantly, helping mitigate climate change by sequestering carbon in the soil and reducing nitrous oxide emissions. So what’s so special about that? Isn’t that what all farming and gardening aims for, or should? I can imagine many readers asking this, especially those already practicing some form of ecosystem-based gardening.

The City of Cahokia, at the confluence of the Mississippi and Missouri Rivers, boasted 20,000 inhabitants in 1200 C.E.
The short answer is, not always or historically. The more than ten thousand year history of agriculture is full of one form of land despoliation or another, which in some cases has brought great civilizations to ruin. Societies in all epochs, on all parts of the earth, from the ancient Romans to the Mississippian-culture city of Cahokia in Illinois, have farmed in ways that have depleted the soil, particularly as population pressures led to more marginal lands being put to use—with logical, disastrous results. Since the European invasion and colonization of the US, modern Americans have continued the ancient tradition of using up a piece of land and then moving somewhere else to begin the process over again. It’s been, in some ways, worse than what ancient cultures did, because, as also in 19th century Australia, the immigrant farmers were trying to replicate what they had known in the vastly different ecosystems of their home countries. Most had little real ecosystem knowledge of the land in which they found themselves and thus no real concept of how to farm it sustainably.

However, even in the 19th century, strong voices were crying out against the ravishment of our grand, beautiful North American continent. While much has been saved, big farmers in the US—and around the world—have continued, and with the use of fossil fuels and agri-chemicals, doubled down, on this civilization-wrecking path: farm fencerow-to-fencerow, expand into marginal lands, deplete the soil and use the available chemicals to attempt to raise fertility…to the logical, disastrous results now in play.

The problem these days, though, is there’s nowhere else to go, for Americans or anyone else. The world is full—overfull—of people and wrecked ecosystems alike. Conquering other countries for their (used up) land or moving to Mars are both equally untenable. (Though you’d never know it from the wars currently in progress and recent propaganda from the pro-space colonization department.) And, meanwhile, the nightmarish specter of climate disruption casts its pall over the earth like the shadow emanating from Mordor.

Alongside this rather dismal history of agriculture, some societies, through trial and error and expert ecosystem knowledge, were able to farm sustainably for centuries, if not always actively improving soil and ecosystem health, at least maintaining it. In large part, these were societies that stayed put—some for thousands of years—and maintained ecologically sustainable populations, either voluntarily, as with birth control and out-migration or involuntarily, as with disease, war, and occasional famine—or some combination. Although some sources show that GHG’s did indeed start slowly increasing at about the time humans invented and began practicing agriculture, they were not a concern, neither known about nor their reduction and sequestration necessary. Unfortunately, as modernization and “conventional” agriculture expanded and became the norm, the traditional ways of land management—crop rotations, milpas and forest gardens, relying on hedgerows and native plant areas to harbor the beneficial insects that helped with pests, and so on, came increasingly under pressure.
A modern day milpa shown at the El Pilar Forest Garden Network website

Often, even as agriculture expanded and industrialized, gardening, or the growing of useful and beautiful plants on small areas adjacent to or near one’s home, has until very recent times tended to hew more closely to the older traditions. In part it may be our innate love of beauty that has long helped keep gardeners moving along a sustainable path, although, as I’ve written elsewhere, that love of beauty has since the 20th century been manipulated by marketing and societal norms into a simplified concept of rigorous control only achievable with the use of industrial strength agricultural chemicals. And modern gardeners and landscapers mostly have conformed, as a visit to any big-box garden center or ride through the suburbs shows, even today. But in gardening, too, there has been strong countervailing interest in and practice of organic and ecosystem-friendly methods.

Why use the term regenerative? What separates it from other forms of ecosystem-based gardening? 
In all, it might seem as though “regenerative” is a new-fangled term in search of an old concept. After all, all these other earth-friendly forms of gardening and farming also consider healthy soil and ecosystems to be the necessary central focus. Much of what regenerative farmers and gardeners are doing has been done before, possibly for centuries, and an emphasis on using scientific measurement and experimentation to help achieve results has also been used for various purposes. The difference is that since the early 20th century, organic methods combining traditional practices with modern scientific knowledge have developed to the point where immense soil regeneration confirmed by good measurement is possible. We now know how much carbon can be stored and that it could give us enough time to transition to a low carbon society.

Perhaps there is something definitively human, some moral and spiritual dimension in this ambition, this desire to right climate and environmental wrongs and heal the earth. To tell someone that one is a regenerative gardener is saying that not only is one practicing ecological gardening in one of its many varieties, but also is doing so with a certain intention. One is gardening in such a way that one is not simply using the earth for one’s own needs and desires, but giving back, fostering the processes, the complicated, complex, four dimensional dance among sun, rain, air; plants, animals, and the life in the soil that will in turn help us mitigate climate change. And what are the practices that make gardening for carbon sequestration different from permaculture, ecological gardening, organic gardening, or reconciliation ecology in general? Maybe simply a subtle shift in emphasis, a slight change in practice, a new attentiveness to the pattern of the dance.

Good rules to garden by
For deep carbon sequestration, the basic requirements are as follows: Help plants maximize photosynthesis and tend the soil biology. Minimize plowing or tilling and digging, grow multi-species polycultures, don’t leave soil bare for extended periods, don’t use pesticides or synthetic fertilizer.

When I was planning this series of posts, I couldn’t decide whether to start the discussion with the plants, the soil or pesticides and synthetic fertilizer. In the real world, as every gardener knows, what we might think of as separate garden topics become inextricably woven together, each strand of the web performing multiple roles, the web formed of multiple relationships. To me, it seems logical to start first with what the would-be regenerative gardener should stop doing and the reasons therefore, before getting into positive practices. Therefore, the discussion will commence with synthetic fertilizer. Not only does its production and transport contribute greatly to GHG emissions, but its long term use also actively lowers soil fertility and prevents carbon sequestration. Fertilizer use contributes to nitrus oxide atmospheric emissions and nitrogen and phosphorus runoff that in turn, contribute to polluted waterways, dead zones along seacoasts and the growth of toxic algae in freshwater lakes and rivers.

As an ecological gardener, I myself have not used either pesticides or synthetic fertilizer for many years, and I’m assuming most of my readers don’t either. When I stopped, I wasn’t thinking about carbon sequestration. I wanted to grow plants organically, and didn’t want my children exposed to toxins. First I learned and practiced a form of integrated pest management, which involves getting to know the insects in the garden, practicing non-chemical controls, and only spraying as a last resort. As I learned more about organic methods such as permaculture, and how to help the ecological balance in my yard I gradually left off chemical inputs altogether. Upon learning about pollinators and beneficial insects and hearing the carbon story, I made more adjustments. My story is an exceedingly common one, yet I talk with plenty of folks who still believe that the gardening year starts with an application of fertilizer, pre-emergent weed killer, fungicides and grub control to their lawn, and continues with herbicides, insecticides and fungicides in the vegetable and ornamental plant beds, and further lawn treatments through the season. (Whole neighborhoods, particularly in well-to-do suburbs, could be classified as biological deserts.) And many people who garden in an environmentally-aware manner may not know exactly how or why synthetic inputs can be so deleterious.

The problem with synthetic chemical fertilizer: what it is, what it does, long-term effects and repercussions 
In his book, The Botany of Desire, Michael Pollan describes the soil in a Midwestern industrial
potato field he visited as gray, dusty, and lacking in good structure. He thought it was the natural soil until he visited an organic potato farm with good dark, friable soil and realized what had been done in the name of farming at the first site. I, myself, noticed this same effect just a few weeks ago when helping plant a row of Osage orange saplings along a property line in central Illinois. On one side was a field long planted to a conventional soy/corn rotation with the ground left bare for the winter after harvest; on the other side, where the trees were being planted, a polyculture of grass, clover and various common lawn weeds, never fertilized, regularly mown, and the clippings left on the ground. On the field side, pale yellow-gray-brown dusty soil. On the grass side, very dark brown clay loam.
A dividing line between healthy and unhealthy soil

Like the soil on the organic farm or my friends’ grassy area, the gray, dusty substance was once well-structured soil full of organic material and teeming with microbes and all the other creatures that form the underground community in healthy soil. What happened? Synthetic fertilizers, among other things. All plants need nutrients, which, since plants first appeared on the scene some 500 million years ago, have been supplied from the earth’s natural systems. This changed in the early 20th century when synthetic fertilizer was invented. The idea was that farming could be more scientific and agricultural yields would increase to feed the world’s beginning-to-burgeon population. The short-term effects were nothing short of miraculous: even previously infertile soils could now grow crops, a boon to farmers and the people they fed.

Fertilizer production didn’t really ramp up until after World War II. A huge supply of ammonium nitrate used for explosives manufacture was left over in munitions factories. (It’s still used for roadside bombs.) With energy and materials from increasingly-available cheap oil and gas, the fertilizer industry took off. Its wonderful effects, coupled with the support of agricultural scientists, the government and large corporations, helped revolutionize farming here and in countries like India and China. This was the fabled ‘Green Revolution” of the 1950's and ‘60's. Naturally, homeowners, landscapers, golf course proprietors and other non-agricultural property owners wanted the stuff and naturally, fertilizer companies were happy to oblige, with the result that U.S. homeowners now use more synthetic chemicals than farmers do in their fields.

Unfortunately, few, other than organic farmers, realized the long-term negative side effects. To begin with, fertilizer manufacture is carbon-intensive and completely reliant on available supplies of oil and gas. Manufacturing not only uses non-renewable resources (and toxic chemicals such as sulfuric acid), themselves extracted, refined and transported in carbon-intensive ways, but the manufacturing and retailing processes involve more carbon use and GHG emissions. To buy a bag of fertilizer is to make a direct contribution to global warming.
Urea fertilizer plant owned by Koch Industries

It turns out, though, that while all plants need nutrients, the way they get them is as important as what they get. Thus, even more important than the benefits of synthetic fertilizers are their deleterious effects on soil structures, on plant-soil creature interactions—and on the planetary ecosystem. As science writer Yvonne Baskin puts it in her book Under Ground, their use (along with pesticides and herbicides) “decouples plants from their dependence on the soil,” so that “the soil does little more than prop up the plants.” Recent scientific studies increasingly confirm what the organic folks have long held.

Researchers at the University of Illinois have shown that continued use of synthetic fertilizers actually causes reduced carbon storage, and thus reduced fertility in the soil, even when organic matter is added. The Morrow Plots at the University of Illinois, Champaign-Urbana have been planted to corn (and other crops) since 1876, the longest continual corn cultivation for the purposes of study in the world. (The Morrow Plots are so important that when U of I built a new library, it was constructed underground so as not to disturb ongoing studies. It’s been rumored that unauthorized student trespass onto the Plots results in immediate expulsion.) Scientist Richard Mulvaney and his colleagues found that from 1904 to 1967, the period when study plots were fertilized with manure, soil organic carbon steadily rose. After the switch to synthetic nitrogen in 1967, soil carbon declined, even though crop residues were incorporated into the soil. Equally surprisingly, nitrogen in the soil declined as well. What was happening?

Apparently, an influx of easily accessed nitrogen causes a soil flora and fauna population explosion. The microbes eat the nitrogen and any organic matter, causing over time a net loss of organic matter and consequent decreased storage of organic nitrogen. Nitrogen-fixing bacteria are negatively affected. Eventually, as organic material is consumed, micro flora and fauna can starve and die. Lacking their multifarious presence, the soil clusters that make up good loam start to break down. Overall soil structure weakens, leading to compaction and increased erosion. Water retention and drainage decline. Salts build up in the soil. Since the soil can no longer store nitrogen efficiently, what it can’t store leaches into groundwater. In Illinois, this leaching has a direct and negative effect on our waterways and contributes to the dead zone in the Gulf of Mexico. The excess nitrogen also enters the atmosphere as nitrous oxide (N2O), a greenhouse gas that can trap 300 times more heat than carbon dioxide (CO2). Ultimately, as researcher Mulvaney told journalist Tom Philpotts in 2009, “the soil is bleeding.”

The upshot? As synthetic fertilizers continue to be used and carbon is lost, the soil’s fertility depletes. Consequently, plants can show less disease resistance, fruits and vegetables show reduced vitamin and protein content, and plants can have difficulty accessing and using other nutrients they need because of the decline in soil life. And, according to soil scientist Christine Jones, plants get “lazy,” ceasing to produce much in the way of the carbon sugars they trade with bacteria and fungi for nutrients through the production of root exudates. This is happening on farms—and, by extension, gardens, around the world.

The farmer and gardener, and the land they tend, become locked in a vicious, addictive cycle. Faced with declining plant vigor, a typical, and for the farmer, seemingly necessary, reaction is to simply add more fertilizer, instead of working to rebuild soil health. These days, this situation is slowly beginning to change as more scientific studies show the value of organic and sustainable farming practices and states like Illinois write new protocols to help conventional farmers reduce fertilizer applications and incorporate conservation practices into their operations. Trends are favorable: for one thing, because of the cost of inputs, and the “organic premium,” studies by Rodale and other long term studies are demonstrating that organic farming actually can be more profitable than conventional farming. Farmers are beginning to pay attention.

Fortunately, we gardeners are not trapped in the destructive logic and ecosystem-ruining requirements of industrial corn and soy production. We can stop using synthetic fertilizer and begin to rebuild soil health right now.

A gradual approach is best for kicking the fertilizer habit 
I don’t exactly remember how I stopped using synthetic fertilizer. Perhaps I simply ran out and never bought more. Perhaps it was as a result of observing how a granular fertilizer spill poisoned the plants in a neighbor’s yard. At any rate, because I had good soil to begin with and had been nurturing good soil health as I understood it at the time, I never noticed much of a difference. Other plants than grass did appear in my lawn, but that has to do more with the no pesticides part of the story. Eventually I learned to maintain my lawn as a polyculture lawn.

In general, going off fertilizer and building natural soil health is a process that takes time—three to five years. It is important not to stop cold turkey because at first there won’t be enough soil life to help plants thrive. Christine Jones recommends tapering by reducing application by 20% the first year, 30% for the two subsequent years and then finally stopping. According to studies done by the Rodale Institute, as fertilizer is reduced, while carbon sequestration practices are followed, during the first three to five years, not much deep carbon is stored. However, after that, the amount of measurable carbon increases over the next thirteen years or so before stabilizing. In ensuing years, increased carbon storage is dependent on even more intensive practice. Multi-species cover crops, no-till planting, use of manure and growing perennials can all help carbon storage continue to increase. 

Jones’ recommendations are for farmers, but gardeners and landscapers should be able to follow this schedule. The 20-30-30 reduction regime would be perfect for lawns, the largest, most heavily fertilized “crop” grown by non-farmers in the US. Like farmers, conventional gardeners should not try to quit all at once, especially if not much has been done to increase organic matter in the soil. Instead, anyone planning to transition should do so gradually, while at the same time changing other gardening practices, including reducing tilling or digging, adding organic matter, and, in some cases, changing the plants being grown. In this way, soil aggregates can form and populations of free-living, nitrogen-fixing bacteria (“associative diazotrophs”), mycorrhizae, arthropods and all the other soil life can increase.

How to avoid fertilizer withdrawal symptoms
Here are a few methods that will help ensure successful fertilizer reduction, some of which will be explored more in depth in coming posts. I’m sure most of my readers already do these things anyway,  and more besides, but in case not, here they are, with the necessary caveat that all gardening conditions are local, indeed, hyper-local.

Lawns: Decreasing the overall size of the lawn in favor of other plantings is a good step to take. In temperate zones such as mine, I don’t advocate getting rid of lawns altogether, since a grassy area is a nice place for a picnic, for children’s play, for paths among garden beds and other recreational uses. Anyone with a lawn can, while tapering off fertilizer, mow high (set the mower at 3”), over-seed with Dutch white clover, and top-dress in fall with finely-sifted compost, as I’ve written here, in “The Polyculture Lawn: A Primer.” Gradually the lawn will begin to function something like a multi-species perennial cover crop and its soil will improve and begin to store carbon.

Planting beds: Increase the size of non-lawn areas as much as possible, use native perennials, shrubs and trees as much as possible, and use mulch judiciously. Anyone who still double digs should just stop, since the idea is to lessen soil disturbance. Learn permaculture and forest garden techniques such as growing edibles, herbs and flowers in the same beds. Large containers are perfect for annuals. Often, at least in my part of the world, something like 80% natives to 20% non-invasive exotics is a fair way to go, for a host of ecological reasons, though I know plenty of native plant gardeners who are serious about their prairie and woodland gardens and only plant natives. And reassess fall clean-up; fallen leaves and other organic “mess” are all soil-building, carbon-storing materials.

Vegetable beds: Here is where some of the advice for farmers can be experimented with more fully, especially if the gardener has a fairly large area. Raised beds benefit by laying on compost and composted manure and then covering with straw. I was going to try a cover crop on my raised bed this year, but since as of this writing I’ve still got chard going and bumblebees still foraging in the heirloom marigolds and calendula, I decided to let things be, and after the first hard frost will amend the soil. Large growing areas, where everything is harvested in the fall, could benefit by frost-killed cover crops sown in the early fall, by use of straw mulch, by the application of composted manure if you don’t have chickens or livestock, and by horizontal, or lasagna-style composting. In the spring, leguminous cover crops/"living mulches" can be planted in the rows between vegetables.
Early October marigolds, tomatoes and bumblebees

Fertilizer is not alone in its threat to soil health and carbon storage. Pesticides, including herbicides, fungicides, and insecticides, pose their own unique dangers to soil biology, as well as to above ground life. This series will continue (with possible interruptions by other posts) with a discussion of some pesticide problems and solutions and will then move on to other topics such as “armoring the soil,” and a deeper discussion of the role of plants.

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Diana Studer said...

this evening I learned how many of the indigenous plants I choose, are edible. That weed I was going to pull, turns out to be dune celery - a good substitute for 'exotic' parsley.

Community gardens with indigenous plants - good news all round!

karen said...

I'm gardening in Australia, where our soils lack a lot of the minerals that synthetic fertilizers attempt to add in. To grow native plants successful it is very important not to synthetically fertilize, but also to watch carefully all additives to the soil - grey water with high levels of phosphorus from detergents, for example. I'm not sure how much this applies to other ecosystems, but being aware of the specific needs of native plants rather than just assume a one-size-fits all model of balanced soil is a good guide generally - and it certainly does discourage synthetic fertilizer use.

Andy said...

Thank you for this pair of excellent posts! In addition to natural growing, I started making and adding biochar to my potting soil. I like carbon sequestration that lasts 1000+ years!