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Carbon, Climate, and Soil Biology

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NRCS Soil Scientist Ray Archuleta admires the soil aggregates present in a vegetable crop field during a workshop at Many Hands Organic Farm on July 25, 2016

photo by Jack Kittredge
NRCS Soil Scientist Ray Archuleta admires the soil aggregates present in a vegetable crop field during a workshop at Many Hands Organic Farm on July 25, 2016

“For most of history, few things have mattered more to human communities than their relations with soil…For the past century or two, nothing has mattered more for soils than their relations with human communities, because human action inadvertently ratcheted up rates of soil erosion and, both intentionally and unintentionally, rerouted nutrient flows.” — Breaking the Sod: Humankind, History and Soil, J. R. McNeill and Verena Winiwarter

Importance of Carbon to Soil

The primary human activity impacting soils is agriculture, and the soil nutrient most severely depleted in quantity by agriculture has been carbon. Conversion from natural to agricultural ecosystems has depleted the soil organic carbon (SOC) pool by as much as 60% in temperate regions, and 75% or more in tropical ones. Such conversion has resulted in losses of 8 to 32 tons of carbon per acre from some soils, mostly oxidized and emitted into the atmosphere as carbon dioxide.

But depleting sinks of soil carbon is harmful in two ways.
Adding carbon dioxide — the primary greenhouse gas — to the atmosphere increases retained solar heat in the planetary system and results in disruptive weather extremes such as we have been experiencing. Since 1975 the global level of greenhouse gases has been rising and average temperature has been increasing at a rate of 0.3˚F to 0.4˚F per decade.
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Conversions, Quantities, Calculations and Indulgences: A Primer

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plant root carbon

Cross-section of a plant root, showing liquid carbon flowing to soil via the hyphae of mycorrhizal fungi. This carbon will support a vast array of microbes that not only retain carbon but also improve soil structure and soil tilth, enhance water-holding capacity, fix atmospheric nitrogen, solubilise phosphorus and provide minerals, trace elements and other growth stimulating substances to plants. Photo courtesy Jill Clapperton

Anyone attempting to make sense of calculations surrounding carbon cycling and soil carbon must first understand a little bit about quantities and conversion factors. Here are some basic facts you might find helpful.

Metric Conversions

First off, much of this literature uses the metric system of measurement. In case you forgot your high school lessons on the metric system, here are some useful conversions.

Length: one meter = 39.3701 inches; one inch (12 in. to a foot, 5280 ft. to a mile) = 2.54 centimeters

Area: one hectacre (10,000 square meters) = 2.4711 acres; one acre (43560 sq. ft.) = .40469 hectares

Volume: one liter (1000 cubic centimeters) = 1.0567 US quart (liquid); 1 US quart (liquid) = .94635 liters
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Why “Carbon Farming”

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Collard greens in mown living legume mulch. This is a great way to build carbon while growing annual vegetable crops.

This issue of The Natural Farmer focuses on the question of how organic farmers in the northeast can adopt methods that build soil carbon. This is a pressing question, as readers of this journal know, because greenhouse gases, primarily carbon dioxide, have been building up in our atmosphere from burning fossil fuels and uncovering soil. Those gases trap solar heat and warm the globe, causing extreme weather events, melting polar ice, and making the planet more and more uninhabitable.

Reversing global warming will require drastic reductions in emissions, which will be a challenge to our consumptive way of life. But reductions will not be enough. Greenhouse gases have long half-lives and will remain active, unless removed, trapping and building atmospheric heat for another century.

To avoid that we need to return much of the carbon that we have taken from the soil. The only feasible method to use for this is the biological process of photosynthesis by which plants use sunlight to break apart carbon dioxide and water, recombining them to form carbohydrates and oxygen. Some of those carbohydrates are exuded by plant roots into the soil and drive an underground ecology that both strengthens plants and sequesters some of that carbon.
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Intensive No-Till at Woven Roots Farm

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photo by Jack Kittredge
Pete Salinetti stands in front of some of the beautiful crops he is growing by precise successions in Western Massachusetts on October 2.

The Berkshires, formed as they were some 300 million years ago by the collision of the supercontinents containing North America and Africa, have had time to adjust. The intense pressure of the tectonic forces that buckled and folded bedrock into fused slabs has dissipated. Millions of years of rain and wind have eroded the jagged peaks that were forced up. Freezing and thawing have cracked and splintered their surfaces. Slowly life has arrived, with its microbial acids and enzymes, and further degraded the rock until now a thin coating of soil covers it and what were mountains are now not much more than steep hills.

The collision has left its mark, however, in exposed geological formations everywhere. Some have attracted the attention of commercial developers and become quarries and mines, especially the deposits of marble and the mile-wide belts of dolomitic limestone present in 500 to 800 foot thick layers. It was the former of these that brought Pete Salinetti’s family to the area over a hundred years ago.

“They were all from Northern Italy,” he explains, “and were fine stone cutters. They ended up in Lee, Massachusetts, cutting slabs of marble. Nobody sells marble there anymore, though. Now they just blow it up and sell it as limestone!”

Pete grew up in Lee, next door to his grandfather, where his family had an extensive garden. He never thought he would farm for a profession, but he loved to garden and grew ornamentals and perennials, including orchard fruit.
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How Biochar Works in Soil

extracted by Jack Kittredge from an article by Kelpie Wilson in the Biochar Journal 2014

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Biochar first came into broad public awareness through the example of the Amazon, where the hypothesis is that Amazonian inhabitants added biochar along with other organic and household wastes over centuries to modify the surface soil horizon into a highly productive and fertile soil called Terra Preta, which is in direct contrast to the typical weathered Oxisol soils in close proximity. Biochar is exciting to many people because of its role in such soil-building processes. Those who have used biochar for several years may obtain tangible positive results, but they may not have solid concepts and theories about how it works. Biochar is a heterogeneous and chemically complex material and its actions in soil are difficult to tease apart and explain mechanistically.
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The Truth About Ruminants and Methane

A NOFA ‘Carbon Paper’ Digest a project to translate scientific papers on soil carbon for the general public.

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The role of ruminants in reducing agriculture’s carbon footprint in North America

This 9-page paper by W. Richard Teague, Steve Apfelbaum, Rattan Lal, Urs P. Kreuter, Jason Rowntree, Christian A. Davies, Russ Conser, Mark Rasmussen, Jerry Hatfield, Tong Wang, Fugul Wang, and Peter Byck was published in the March/April 2016 Journal of Soil and Water Conserva-tion, vol. 70, no. 2, page 156

Summary: This scientific paper argues that the co-evolution of grass and ruminant grazers over the last 40 million years resulted in organisms capable of sequestering large amounts of atmospheric carbon in grassland soils. When measured in greenhouse gas (GHG) units, their sequestration exceeded GHG emissions (including emissions of methane) caused by these grazers, resulting in net soil carbon gains.

Argument: The authors collected data from peer-reviewed studies to compare global GHG emissions from the 3 main agricultural sources: raising domes-tic livestock (primarily ruminants), crop production (including tillage, fertilization, harvest and transport) and soil erosion (from both livestock and crop operations). They also evaluated methods of managing ruminants to increase carbon sequestration in soil.
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Farming with Animals, Cover Crops, Manure, Mulches, and Minimal Tillage

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photo by Jack Kittredge
Julie Rawson in West Field at Many Hands Organic Farm, admiring some kale and broccoli

Central Massachusetts is not what you would call prime farmland. Like most of New England that isn’t blessed with a nearby waterway and thus alluvial deposits, our soils are thin and only farmable where the underlying landforms aren’t too rocky, hilly or wet to grow crops.

When Julie and I bought this land 36 years ago it was composed of two played-out hayfields that had been de-rocked years ago and about 30 acres of woods that had not. Since then we have put drain tile under the fields to get them plantable by April, brought or grown onto them uncountable tons of organic matter to build soil, and hauled from them an equal volume of rocks that the first team of de-rockers somehow missed. We have yet to deal with the underlying abundance of potter’s clay and ledge.

The big advantage to central Massachusetts, we told ourselves, was that the land was so unattractive to farmers that we didn’t have to worry about spray drift or chemical contamination by neighbors, a huge concern where Julie grew up in Illinois.

Since then we have built a serviceable farm here, certified organic since 1987 and are providing produce and small and orchard fruit through a CSA to some 60 families currently, and to several wholesale accounts. We also raise a number of animals and sell meat and eggs, mostly to individuals.
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IFOAM’s André Leu to Keynote NOFA Summer Conference:

Reversing Climate Change and Improving Farms

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André Leu, president of IFOAM, to keynote 2016 NOFA Summer Conference

André Leu, president of IFOAM, to keynote 2016 NOFA Summer Conference

André Leu is both a farmer and an advocate. With his family André operates a 150-acre fruit farm in tropical Australia. Once defeated and run down, his farm is now a lush and productive permaculture landscape, a system designed to minimize inputs and labor and maximize productivity, nutrient recycling and biodiversity.

For over 10 years he has been influencing international climate change policy, not only drawing attention to the role of soil in absorbing carbon to mitigate existing climate chaos, but also demonstrating how organic agriculture can help farmers and societies adapt to the effects of climate change. After the November 2015 Paris Climate Change Conference, he sees this as a critical time to galvanize nations to agree to include shifts in farming policies in their agreements and pledges and to see those pledges from idea to action.
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