A frequently used—at least, by soil scientists—definition for soil health is “the continued capacity of soil to function as a vital living system […] to sustain biological productivity, maintain the quality of air and water environments, and promote plant, animal, and human health” (Doran et al. 1996). Many different indicators—chemical, physical, and biological—are used to assess soil health.
Figure 1. Potatoes are economically important crops in many irrigated areas of the Pacific Northwest. Here, potatoes are harvested near Pasco, Washington. Photo: Athena Loos.
Growing potatoes is notoriously hard on the physical and biological health of soil (Figure 1). Potato production in many areas of the Pacific Northwest involves seven or more soil disturbance operations, leaves little residue on the field, and often involves the use of fumigants to control soilborne diseases. The economics of potato production often drive growers to utilize short rotations. But a suite of strategies are possible to improve soil health in potato production, including cover crops, rotating with perennial crops and crops that contribute high levels of residues, and incorporation of organic amendments. While growing green manure crops for biofumigation has probably achieved the most success and adoption in the region (see producer Dale Gies as an example), in this article I focus on a more challenging strategy that has received limited attention, but may have more direct climate change implications: tillage reduction. Continue reading →
Like other ecosystems, forests store carbon both above and below ground. Photo: Chris Schnepf.
Ten years ago, when I visited with forest owners about climate change, there was a fair amount discussion about what was happening or not, and all the politics surrounding it. But one of the topics landowners were intrigued about—regardless of the extent to which they believed climate was changing—was carbon markets. Forest owners were excited about the prospect of a revenue stream for things they were doing well on their forest, that would result in more carbon being sequestered.
The connection between soil health and carbon sequestration are complex, but advances in soil biology are teasing them out. Photo: Ron Nichols/USDA NRCS under CC BY 2.0.
A number of recent AgClimate.net articles focused on soil health (see for example this article on a soil health NRCS resource and one on decomposition of wheat residues research). These articles commented on why soil health is important from a climate change perspective: more carbon-rich organic matter in the soil contributes to soil health, and also means less carbon as carbon dioxide in the atmosphere. So the potential exists for a win-win situation. As most things in life and agriculture, the connections between improved soil health and increased carbon sequestration are not as simple as they sound. Check out Andy McGuire’s elegant blog article describing why advances in soil biology—a foundational component of soil health—are important. He explains that it is not because they “change everything,” but because they help clarify why some things work and some don’t as much, and explain how complex that connection between soil health and carbon sequestration in soils appears to be. And though we may not want to hear it, we need this understanding to determine where the win-win practices that both increase soil health and sequester more carbon might realistically be. So take a few minutes to read McGuire’s article—it’s well worth the time!
Healthy soils can build greater resilience and reduce risks in the face of more extreme and variable weather. Photo: Aaron Roth/NRCS under CC BY-ND 2.0.
Climate change is expected to increase the vulnerability of our agriculture and natural resource systems. In the face of more extreme and variable weather, there are a suite of soil health management practices that land managers can adopt to build greater resilience and to reduce risks in their agricultural operations (examples of strategies in Figure 1).
Through engagement with land managers and those who work with them, including Extension, Natural Resource Conservation Services (NRCS), and Soil and Water Conservation District (SWCD) professionals, it became clear that many of them were interested in soil health and its linkages with climate change adaptation and mitigation. As a result, Oregon NRCS and the USDA Northwest Climate Hub partnered to develop a resource to aid advisors and land managers in discussing soil health and climate resilience together. Continue reading →
Managing crop residue is essential to reduced and no-till farming systems. These farming systems store more carbon than conventional farming systems, thereby mitigating climate change, enhancing soil health, and reducing soil erosion. In work described in a recent project report, Arron Carter and colleagues have been working to make it easier for growers with diverse needs across the Pacific Northwest to manage wheat residues. While the work is still in progress, it is an illustration of the kind of creative, applied work that is needed to make reduced-tillage systems easier to manage, and more widely adopted across the region.
Wheat residue in a field in early July near Bickleton, WA. This area is part of the drier winter wheat-fallow area, where slower decomposing residues are preferred. Photo: Hilary Davis.
Growers in different parts of the dryland Pacific Northwest are seeking different residue characteristics. Continue reading →
Biochar has the potential to sequester carbon and improve the properties of soils when used as an agricultural amendment. However, biochar will only be a viable option for carbon sequestration if there are uses and viable markets for this biochar. In recent years, there has been interest in adding biochar to agricultural soils in conjunction with compost, and in some cases, “co-composting” biochar—putting the biochar in with the feedstock before the composting altogether. Read on to learn about a study led by Dr. David Gang, a professor at Washington State University’s Institute of Biological Chemistry, indicating that co-composting can provide additional benefits, both during the composting process and to the crops grown in soil amended with the resulting co-composted biochar.
Figure 1. Mark Fuchs (left), John Cleary (right) (both of the Washington Department of Ecology) and Nathan Stacey (middle, WSU) use equipment to measure gas emissions from a commercial scale co-composting experiment. Photo: Doug Collins, WSU.
A number of our articles this year discussed using biochar in agriculture and in forestry. These earlier articles did not delve into the methods to apply biochar on large tracts of forests. You’d expect this to be a much more challenging task than spreading biochar on croplands. Researchers and technology developers are tackling this particular issue, developing a specialized forest biochar spreader. Take a few minutes to check out their Science Spotlights article and their video. Among the details they discuss in the video is a point Chris Schnepf and Darren McAvoy made in their AgClimate article: biochar can use—and store the carbon that is in—those “leftovers” that otherwise get burned, releasing that carbon into the atmosphere.
Topsoil has often been referred to as the “thin skin” of our planet, essential for producing the food that feeds us. Because it’s not easy to create new topsoil, conserving the soil that we have is essential for maintaining our region’s agricultural productivity. Reducing tillage, and leaving residue on the soil surface, is a proven way to reduce erosion. As residues break down, they increase the concentration of soil organic matter at the surface of the soil and help to form soil aggregates—a composite of soil particles that clump or bind together, giving soil its structure. Soil that is aggregated in larger particles is less prone to being eroded by the wind. And soils with more organic matter also benefit the climate, by storing more carbon.
Planting the wheat cover crop in strips makes planting corn easier, as the planter does not encounter roots and leaves in the planting strip. Photo: Darrell Kilgore
In non-irrigated areas that are too dry to support annual cropping, fallow (the practice of leaving land unplanted) preserves soil moisture for future crops. However, annual fallow combined with conventional tillage has resulted in a net decrease in soil carbon over time in our region, with negative impacts to soil health across large areas. And even when tillage is eliminated, it is very difficult to maintain soil carbon over time in a wheat-fallow system. For this reason, the impact of climate change on the frequency of fallow in crop rotations has important future implications both for soil health and for opportunities for carbon sequestration.
Two papers published last year by Kaur et al. and Karimi et al. use modeling to project the impacts of climate change on dryland cropping systems. Continue reading →
What are the climate impacts of a given farm practice? While we know lots of strategies for reducing greenhouse gas emissions on farms, quantifying that impact can be difficult. However, there is at least one farm in our region – one that uses some pretty neat practices – for which scientists have attempted to answer that question. And the farmer just happens to be a long-time member of the Center for Sustaining Agriculture and Natural Resources’ advisory committee, Dale Gies. Continue reading →