Increased soil carbon increases crop yield — to a point

They found that the largest gains in yield occurred between concentrations of 0.1 percent and 2 percent of soil organic matter.
“…we now have numbers, not just unverified ideas, that if you build organic matter you can improve outcomes — such as less fertilizer and increased yield.”

Yale School of Forestry & Environmental Studies Read Science Daily article here 

  • Emily E. Oldfield, Mark A. Bradford, Stephen A. Wood. Global meta-analysis of the relationship between soil organic matter and crop yieldsSOIL, 2019; 5 (1): 15 DOI: 10.5194/soil-5-15-2019

While policymakers often tout the benefits of increasing soil organic matter as a way to boost agricultural yield, there is limited evidence that this strategy actually works. A new study quantifies this relationship, finding that greater concentrations of organic matter indeed produce greater yields — but only to a certain point.

Specifically, they find that increasing soil organic carbon — a common proxy for soil organic matter — boosts yields until concentrations reach about 2 percent, at which level they tend to hit a saturation point. Thereafter, the researchers say, the increase in SOM begins to deliver diminished returns.

Even still, they find that roughly two-thirds of agricultural soils dedicated to two of the world’s most important staple crops — maize and wheat — fall below that 2-percent threshold, suggesting the vast potential for agricultural policies that promote increased soil organic matter.

…It is well understood that building and maintaining soil organic matter is key to soil health. (SOM refers to organic matter found in the soil, including plant and animal materials that are in the process of decomposition.) It strengthens the capacity of soils to retain water and nutrients, supports structure that promotes drainage and aeration, and helps minimize the loss of topsoil through erosion.

For years, policymakers have emphasized the role of soil organic matter in a series of programs, including the “4 per 1,000” initiative of the Soils for Food Security — which emerged from the COP21 negotiations — and the U.S.’s “Framework for a Federal Strategic Plan for Soil Science.”

And yet when it comes to its role in promoting crop production, there’s been a surprising dearth of quantitative evidence, Bradford says. For Bradford, this gap in knowledge has been a nagging concern for nearly a decade; a 2010 National Research Council report on sustainable agriculture described organic matter as the cornerstone of most sustainability and soil quality initiatives, he recalls, yet offered no information on how much was actually needed to increase crop yields and reduce fertilizer application.

Agrivoltaics: Solar Panels on Farms Could Be a Win-Win

Massachusetts is leading the charge in dual-use solar installations, making it possible to grow some crops and pasture animals while generating clean energy.

By Sarah Shemkus Read full Civil Eats article here

he solar panels in the fields at the University of Massachusetts Crop Research and Education Center don’t look like what most of us have come to expect. Instead of hunkering close to the earth, they’re mounted seven feet off the ground, with ample room for farmers or cows to wander underneath. Panels are separated by two- and three-foot gaps, instead of clustering tightly together. Light streams through these spaces and, underneath, rows of leafy kale and Brussels sprouts replace the typical bare earth or grass.

This unusual arrangement is one of the first examples of a dual-use solar installation—sometimes called agrivoltaics. It’s a photovoltaic array that’s raised far enough off the ground and spaced in such a way that some crops can still grow around and beneath the panels. The goal is to help farmers diversify their income through renewable energy generation, while keeping land in agricultural use and reducing greenhouse gas emissions….

A global agenda for collective action on soil carbon

Policymakers and investors have perceived securing soil organic carbon as too difficult, with uncertain returns. But new technical, policy and financial opportunities offer hope for rapid progress.

Sonja Vermeulen, Deborah Bossio, Johannes Lehmann, Paul Luu, Keith Paustian, Christopher Webb, Flore Augé, Imelda Bacudo, Tobias Baedeker, Tanja Havemann, Ceris Jones, Richard King, Matthew Reddy,
Ishmael Sunga, Moritz Von Unger and Matthew Warnken. Nature Sustainability | VOL 2 | JANUARY 2019 | 2–4 | Read full NATURE article here and Nature4Climate article here (and below)

“It’s too hard and too uncertain,” has long been the response of policymakers and investors in response to working on ways to conserve and improve carbon in soil. But, recent new momentum summarised in a paper in Nature Sustainability and authored by actors from government, science and the private sector offers hope in the form of technical, policy and financial opportunities for rapid progress.

Building soil organic carbon helps water cycling, agricultural productivity, as well as climate change mitigation and adaptation. The amount of soil carbon globally is triple that of the atmosphere, making soil a useful tool for combatting climate change. A new global analysis … shows that building soil organic carbon on all corn and wheat lands could close the yield gaps for those crops by between 1/3 and 2/3 while also minimizing dependence on synthetic fertilizers.

“Momentum for action on soil organic carbon is indeed growing in political, financial and technical circles to address multiple sustainability goals, but not nearly fast enough.” says Deborah Bossio, Lead Soil Scientist at The Nature Conservancy and co-author of the paper published in Nature Sustainability.  Authors of the paper conclude that ‘a clear focus on early wins and on continued collaboration will lay the ground for gains in soil organic carbon at scale within an urgent timeframe.’

Under the UN Climate Convention (UNFCCC) only eight countries include targets for soil organic carbon within their intended mitigation options – (Armenia, Burkina Faso, China, Japan, Malawi, Namibia, Uruguay and Zambia). That said, a few have policies that support stronger action, ranging from Canada, which recognizes the potential of soil organic carbon under conserved forests and wetlands, to Bhutan, with its sustainable soil policy.

In addition, new financing instruments are emerging to support better environmental management of soils beyond climate concerns, such as funds (for example, the Land Degradation Neutrality Fund, managed by Mirova, and Clarmondial’s Food Securities Fund) and loan programmes (for example, the Rabobank and UNEP Kickstart Food programme).

Pioneering initiatives – both regulatory and voluntary – at national and sub-national levels, also provide evidence of economic viability and rapid results at the local level. Australia and California are examples of early adopters of market-based approaches to raising soil organic carbon. Australia’s Carbon Farming Initiative, a legislated voluntary offsets scheme implemented by the Emission Reduction Fund, has awarded contracts with an approximate value of A$200 million to landholders and farmers to earn carbon credits from soil organic carbon projects on degraded land, supporting a wide range of activities from rotational grazing to reduced tillage.

In the private sector, a growing number of companies are also including soil organic carbon within their set of options to build resilience and long-term profitability of agricultural value chains. Danone, Mars, Bayer, Coca Cola, Fonterra, Diageo and Olam are multinational examples.

“We need a new mindset,” said Deborah Bossio. “We need to give up on the idea that it’s all too hard. To combat climate change and to produce healthy diets, we need every tool in the toolbox. We might not think about soil all the time, but boy we notice it when it’s gone.”

Climate change tipping point could be coming sooner — Vegetation and soil may not be able to sequester as much carbon due to variability in soil moisture

A net gain of carbon on the land surface, would actually be almost twice as high if it weren’t for the variability in soil moisture

Columbia University School of Engineering and Applied Science Read full ScienceDaily article here

  • Julia K. Green, Sonia I. Seneviratne, Alexis M. Berg, Kirsten L. Findell, Stefan Hagemann, David M. Lawrence & Pierre Gentine. Large influence of soil moisture on long-term terrestrial carbon uptakeNature, 2019 DOI: 10.1038/s41586-018-0848-x

A new study confirms the urgency to tackle climate change. While it’s known that extreme weather events can affect the year-to-year variability in carbon uptake, and some researchers have suggested that there may be longer-term effects, this study is the first to actually quantify the effects through the 21st century and demonstrates that wetter-than-normal years do not compensate for losses in carbon uptake during dryer-than-normal years, caused by events such as droughts or heatwaves.

…Anthropogenic emissions of CO2 — emissions caused by human activities — are increasing the concentration of CO2 in the Earth’s atmosphere and producing unnatural changes to the planet’s climate system. The effects of these emissions on global warming are only being partially abated by the land and ocean. Currently, the ocean and terrestrial biosphere (forests, savannas, etc.) are absorbing about 50% of these releases — explaining the bleaching of coral reefs and acidification of the ocean, as well as the increase of carbon storage in our forests.

“It is unclear, however, whether the land can continue to uptake anthropogenic emissions at the current rates,” says Pierre Gentine…

Global-scale evaluation of role of soil minerals in carbon storage

University of California – Santa Barbara Read ScienceDaily article here

Marc G. Kramer, Oliver A. Chadwick. Climate-driven thresholds in reactive mineral retention of soil carbon at the global scaleNature Climate Change, 2018; 8 (12): 1104 DOI: 10.1038/s41558-018-0341-4

One answer to our greenhouse gas challenges may be right under our feet: Soil scientists have found that minerals in soil can hold on to a significant amount of carbon pulled from the atmosphere. It’s a mechanism that could potentially be exploited as the world tries to shift its carbon economy. …

… Wetter climates are more conducive to formation of minerals that are effective at storing carbon, therefore much of the Earth’s estimated 600 billion metric tons of soil-bound carbon is found in the wet forests and tropical zones. Arid places, meanwhile, tend to have a “negative water balance” and can thus store far less organic carbon. According to Chadwick, the findings suggest that even a small, strategic change in the water balance could drive greater carbon storage.

… There is still a lot to investigate and several hurdles to overcome as soil scientists everywhere consider ways to tip the balance of the Earth’s soil from carbon source to carbon sink, but according to these researchers, understanding this relatively little-known but highly significant carbon storage pathway is a start.

Seagrass saves beaches and money

Read full ScienceDaily article here

Rebecca K James et al. Maintaining Tropical Beaches with Seagrass and Algae: A Promising Alternative to Engineering SolutionsBioScience, 2019; DOI: 10.1093/biosci/biy154

Seagrass beds are so effective in protecting tropical beaches from erosion, that they can reduce the need for regular, expensive beach nourishments that are used now. In a recent article in the journal BioScience, biologists and engineers from The Netherlands and Mexico describe experiments and field observations around the Caribbean Sea. “A foreshore with both healthy seagrass beds as well as calcifying algae, is a resilient and sustainable option in coastal defense,” says lead author Rebecca James, PhD-candidate at the University of Groningen and the Royal Dutch Institute for Sea Research (NIOZ), The Netherlands. “Because of erosion, the economic value of Caribbean beaches literally drains into the sea….

Does Grazing Matter for Soil Organic Carbon Sequestration in the Western North American Great Plains?

Long-term removal of grazing from semiarid grassland ecosystems in the western North American Great Plains does not enhance long-term SOC sequestration.

Justin D. Derner, David J. Augustine, Douglas A. Frank. Ecosystems (2018).


Considerable uncertainty remains regarding grazing-induced influences on soil organic carbon (SOC) sequestration in semiarid grassland ecosystems due to three important complications associated with studying such effects: (1) Ecologically meaningful shifts in SOC pools attributable to grazing are difficult to detect relative to inherently large grassland SOC pools, (2) a lack of baseline (pre-treatment) data, and (3) frequent lack of or limited replication of long-term grazing manipulations. SOC sequestration rates were determined in 74-year-old grazing exclosures and paired moderately grazed sites, established across a soil texture gradient, in the western North American shortgrass steppe in northeastern Colorado. We sampled soils (0–20 cm) from 12 exclosures and paired grazed sites to measure SOC concentration and soil radiocarbon D14C (&); the latter allowed us to determine turnover of the SOC pool over a 7-decade period in the presence versus the absence of grazing. Removal of grazing for more than 7 decades substantially altered plant community composition but did not affect total soil C, SOC, soil D14C, SOC turnover rate, or total soil N. Grazing effect also did not interact with soil texture to influence any of those soil properties. Soil texture (silt + clay content) did influence total soil C and SOC, and total soil N, but not D14C or SOC turnover. Results provide evidence that long-term removal of grazing from semiarid grassland ecosystems in the western North American Great Plains does not enhance long-term SOC sequestration, despite changes in the relative dominance of C3 versus C4 grasses.

Carbon Market Incentives to Conserve, Restore and Enhance Soil Carbon

September 2018  Read full report here and summary here

Soils rich in organic carbon are associated with enhanced agricultural productivity, water cycling, biodiversity and climate change adaptation and mitigation. But despite the important role they can play in fighting climate change, to date soils have largely been missing from carbon markets.

There are signs that the future may be more promising. This study assesses the specific situation of soil carbon—its position in climate policymaking, the specific challenges, and the opportunities for intervention. It does so to explore to what extent carbon project finance tools can help advance the ability of soil carbon to make a meaningful contribution to climate change mitigation, providing multiple co-benefits. By taking the voluntary market as the lens, it also serves to inform the wider fate and utility of land sector carbon projects within the evolving political framework of the Paris Agreement.

Deborah Bossio, TNC, was a consultant on this project.

von Unger, M. & Emmer, I. (2018). Carbon Market Incentives to Conserve, Restore and Enhance Soil Carbon. Silvestrum and The Nature Conservancy, Arlington, VA, USA

How we can make beef less terrible for the environment- managed grazing with silvopasture (Wash Post Opinion)

Eric Toensmeier is a lecturer at Yale University and a senior researcher with the climate change-focused nonprofit Project Drawdown. He is the author of “The Carbon Farming Solution.” Read full Washington Post opinion piece here.

Long-term storage of carbon in silvopasture soil is up to five times higher than managed grazing alone — not to mention the carbon stored in the biomass of the trees, although this is not a solution for all rangelands.

When I began investigating how to capture carbon dioxide to fight climate change a decade ago, I had no way of knowing which tool would have the greatest potential. Years later, in 2015, when the environmentalist and entrepreneur Paul Hawken hired me to work for Project Drawdown to help model the impacts of 23 land-based climate change solutions, many on our team were surprised when a relatively unknown solution called “silvopasture” emerged as the most powerful agricultural production practice — the ninth most powerful method overall.

Silvopasture systems combine trees, livestock (ruminants like cattle, sheep and goats) and grazing. Ranchers and pastoralists plant trees or manage the land for spontaneous tree growth. The trees provide shade, timber and food for livestock. In most silvopasture systems, the carbon captured in soil and trees more than makes up for the greenhouse gases (methane and nitrous oxide) that ruminants emit through belches and flatulence. One study of intensive silvopasture in Colombia found that emissions from livestock were equal to a quarter to half of the carbon sequestered in soil and biomass…..

Soils & climate: from hidden depths to centre stage

by Sonja Vermeulen See full Chatham House article here

Soils offer a major share of the world’s actual and potential carbon storage. Globally, the top 30 cm of soil hold about double the carbon in the atmosphere, and more than that in all the forests and sunlit ocean layer combined. Increasing carbon in soils is potentially an effective means of reducing levels of carbon dioxide in the atmosphere and in oceans, while providing positive co-benefits, particularly for food security.

Globally soils have the potential to store 6 billion tonnes of CO2 per year. 

Management practices that increase soil organic carbon are largely very low in cost compared to alternative greenhouse-gas abatement options. Scientists and policymakers broadly agree that soil organic carbon can deliver climate-change abatement while helping meet various goals in food security, sustainable development, economic growth and equity. Soils have a carbon-sequestration potential as high as six billion tonnes a year globally, though a more conservative estimate is in the order of a billion tonnes a year, which is about a tenth of total annual emissions of greenhouse gases from all sources. On the back of optimism about them, there is growing visibility for soil organic carbon solutions.

Momentum for action is gathering in political, financial and technical circles. Political headway at the global level is growing through avenues such as the 4 per 1000 Initiative, the 2017 agreement on agriculture under the United Nations Framework Convention on Climate Change (UNFCCC) that explicitly refers to soils, and the central role of soils in the UN Sustainable Development Goals target on land degradation neutrality that is linked to the United Nations Convention to Combat Desertification (UNCCD). Financial support is following this political momentum, with new funds such as the Land Degradation Neutrality Fund and the Kickstart Food Fund launched in 2017. Technical momentum includes substantial work on mapping soil organic carbonsharing soil information and developing cost-effective measurement systems.

Pioneering initiatives around the world provide evidence of economic viability and rapid results (see carousel). A mix of regulatory and voluntary initiatives at national and sub-national levels provide timely lessons for global upscaling of action on soil organic carbon. Early adopters of market-based approaches to increasing soil organic carbon include Australia and California. While only eight UNFCCC Nationally Determined Contributions (NDCs) present targets for soil organic carbon within their intended mitigation options (Armenia, Burkina Faso, China, Japan, Malawi, Namibia, Uruguay and Zambia), many countries have policies that support stronger action. They range from Canada, which recognizes the potential of soil organic carbon under conserved forests and wetlands, to Bhutan with its sustainable soil policy, and France, which has soil health through agro-ecological principles at the heart of its 2014 Law on the Future of Agriculture, Food and Forestry.