Thistle in Orchards
40 Acre Co-op
Interseeding Cover Crops
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TM
Volume 29 | Number 2
Midwest Organic & Sustainable Education Service
March | April 2021
Researchers use 30-year cropping systems experiment to evaluate if farm fields can serve as carbon sinks By Randy Jackson, Gregg Sanford, Matt Ruark, Anna Cates, Ashley Becker, Yichao Rui, David LeZaks
There’s a palpable buzz around soil carbon in the agricultural community. It’s exciting to see so much attention and energy directed toward addressing climate change and, in particular, so much exploration about how agriculture can be part of the solution rather than part of the problem. Investment organizations are clamoring to find the scheme where their capital will “do good.” Policymakers are scrambling to develop incentive mechanisms for practices believed to build soil carbon. Farmers are touting their management for soil health and carbon accumulation. With this backdrop, a panel discussion at the Growing Stronger Conference explored the evidence that agricultural soils might help draw down atmospheric carbon dioxide levels to help slow climate change. Relying mostly on results from a long-term experiment at Arlington Agricultural Research Station in south-central Wisconsin—the Wisconsin Integrated Cropping Systems Trial (wicst.wisc.edu)— Dr. Randy Jackson relayed the group’s overall message: Tweaking our dominant grain-based annual crops with reduced tillage, cover crops, and manure addition is not likely to make those systems atmospheric carbon sinks (Fig. 1).
Fig. 1. Twenty-year differences in soil organic carbon (1989 to 2009) across entire soil depth (~3 ft.) at the Wisconsin Integrated Cropping Systems Trail (WICST). Crops on x-axis from L to R: (1) high-input continuous corn, (2) high-input corn-soybean rotation, (3) organic corn-soybean rotation with wheat cover crop, (4) high-input corn-alfalfa rotation, (5) organic corn-alfalfa rotation with oat cover crop, and (6) cool-season pasture with managed rotational grazing (modified from Sanford et al. 2012 Agriculture, Ecosystems & Environment).
Data shared by the group indicated that agriculture based on perennial grassland was our best and perhaps only approach to building soil carbon, although even pasture was struggling to maintain soil carbon stocks over the 20-year period (Fig. 1). Hypotheses for this lack of significant carbon accumulation in their grassland plots included the inherently shallow roots of cool-season pasture grasses and feedback from the already changing climate. During the discussion period following the panel presentations, attendees speculated that perhaps carbon would accumulate in deeper soils if warm-season grasses from the tallgrass prairie, known for their deeper roots, were grazed. Dr. Gregg Sanford described why the soil carbon balance of an agroecosystem is so precarious. Data show that only 3 or 4 months of the year are periods when the input of carbon from the atmosphere via photosynthesis is greater than the output of carbon to the atmosphere from soil microbes. He also addressed the importance of deep soil sampling over time to accurately represent soil carbon change. Sanford showed how most of the “short-cut” methodologies for estimating change can result in questionable findings that tend to inflate estimates of soil carbon change. Dr. Matt Ruark shared results of a soil carbon survey on organic grain farms concluding that the most important indicators of high soil carbon were whether the soils formed under prairie (that is, Mollisols) and whether recent management included pasture. Then, Dr. Anna Cates explained why establishing cover crops in the upper Midwest is so difficult. She described narrow windows each fall between main-crop harvest and temperatures that are too low for cover crop germination. Dr. Cates made clear how important cover crops are for soil and nutrient retention and reducing runoff, but showed how the amount of cover crop biomass is directly linked to whether it shifts the soil carbon balance of a cropping system. Ashley Becker shared preliminary data from a survey of over 30 grazing farms in southern and central Wisconsin. Grazed pastures had almost 5 tons more carbon per acre in the surface 6 inches of soil than nearby sites on similar soil types under annual crop Farms as Carbon Sinks continues on 6
Virtual mega-conference draws farmers’ praise; access still available to recordings By Audrey Alwell
The Growing Stronger Conference combined the MOSES Organic Farming Conference, GrassWorks Grazing Conference, OGRAIN Organic Grain Conference, Midwest Organic Pork Conference, and Organic Vegetable Production Conference into one week-long event at the end of February. More than 1,600 people attended the mega-conference, which is still open for on-demand viewing through late May. Farmers have been enthusiastic about the event. Here’s a sampling of what they’ve shared: “The Growing Stronger Conference was incredible with a wide variety of topics and very knowledgeable speakers who really went into great detail on their area of expertise.” Jennifer Eis, Dreaming Field Farm “I got ideas for my hemp, bees, goats, and chickens— I have a notebook full of ideas to start putting into practice this spring!” Robyn Bindrich, Valley Girls Farm “The topics were what I was looking for and more. Access to workshops post-conference is making all the difference. I felt I could do urgent things around the farm and still be able to attend later.” Mike Miles, Anathoth Community Farm People who missed the live event still may register to watch over 120 hours of recorded workshops, roundtables, and keynotes. For descriptions and registration details, see https://bit.ly/GrowingStronger2021. Post-conference registration closes March 31 to allow time to view recordings before the end of May. Growing Stronger Conference continues on 6
No-till, cover crops don’t ensure net soil carbon gains; integrated crop-livestock systems should be incentivized
PO Box 339, Spring Valley, WI 54767
By Nicole Tautges, Ph.D.
Interest in buying and selling carbon credits from agricultural lands is rapidly ballooning among the farm and business community. Farmers are looking to carbon credits as a new opportunity to increase farm revenues and profitability, to subsidize the sustainable practices (like cover cropping and perennial cropping) that aren’t as profitable or cost more than conventional row cropping with corn and soybeans. But perhaps most of all, farmers are looking for ways they can be financially compensated by society for performing land management practices that protect and enhance ecosystem services—in other words, the ways that natural or ecological functions benefit humans, like water filtration, clean air, biodiversity, and, importantly for climate change, soil carbon storage. On the other end of the value chain, large corporations in the U.S. are centering their short- and long-term goals around sustainability and climate
change mitigation, with most pledging to achieve “net zero carbon emissions” in one to two decades. These companies have earmarked significant dollars to achieve these goals and, while they are unlikely to cut their fossil fuel emissions entirely, they are looking to purchasing carbon credits to offset the carbon emissions associated with their activities. This has led to formation of carbon markets that “find” carbon storage mechanisms and sell them to carbon buyers. Nori1 and IndigoAg2 are the two most recent and notable startups buying carbon credits from farmers (surviving for the meantime on investor funding), as farmland is seen as having large potential for greenhouse gas emission offsetting and atmospheric CO2 drawdown. On IndigoAg’s platform, farmers can earn up to $30/acre/year and $50/acre/year on Nori’s platform for adopting practices like no-tillage, cover Soil Carbon Gains continues on 8