The Soil Organic Carbon network (SOCnet): Farmers building soil assets to help mitigate and adapt to climate change in the North Central US

Progress report for LNC22-475

Project Type: Research and Education
Funds awarded in 2022: $249,738.00
Projected End Date: 10/31/2025
Grant Recipient: UW-Madison
Region: North Central
State: Wisconsin
Project Coordinator:
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Project Information


Climate change is an existential threat to humanity. Unpredictable and extreme weather puts significant pressure on farmers to produce food and feed for a growing population while simultaneously dealing with fluctuating yields, erratic markets, and unreliable income. Building soil organic carbon (SOC) provides a means of increasing on-farm climate resilience. As SOC accumulates, soil structure and water holding capacity improve, nutrient retention and mineralization increase, and soils are protected from the devastating effects of erosion1. What’s more, the world’s agricultural soils, depleted by centuries of extractive management, have a large capacity to sequester atmospheric carbon dioxide and mitigate climate change2. Public and private efforts are constructing markets to compensate farmers for soil carbon sequestration, but accurate assessment is critical to de-risking these efforts. Short-term assessments of surface soils and the use of space as a surrogate for time dominate most efforts to track soil carbon, but these approaches lack the scientific rigor required to assess SOC accrual or loss. Carbon sequestration is a slow and variable process that requires long-term monitoring of entire soil profiles while accounting for potential alterations to bulk density to accurately track change. The Soil Organic Carbon network (SOCnet), a farmer-scientist collaboration, will help to build on-farm resilience to climate change and prepare farmers to engage in emerging carbon markets by evaluating farming practices designed to build SOC and accurately tracking their effectiveness. SOCnet puts control in the hands of famers rather than the private sector and will set the standard for accurate accounting of soil carbon credits. SOCnet will link producer-driven on-farm research throughout the North Central US with long-term cropping systems experiments in Wisconsin, Iowa, and Minnesota. These long-term experiments play a critical role in our understanding of SOC sequestration in the prairie-derived soils of the US Corn Belt. However, because SOC dynamics are strongly influenced by soil and climate factors, multi-location assessment is needed, and on-farm collaborative experimentation is ideal for addressing this limitation. SOCnet will focus on farmer-to-farmer knowledge transfer through state and regional field days and regular network meetings, fostering growth over time. SOCnet will empower farmers by creating tools to track, interpret, and document on-farm carbon stocks to meet their soil health goals, build resilience, and prepare for carbon market opportunities. The knowledge generated though SOCnet will further serve to inform state and local government planning and policy development throughout the North Central US.

Project Objectives:
  1. Evaluate the carbon sequestration potential of alternative farming through long-term monitoring of SOC stocks on-farm and Long-term experiments throughout the North Central Region.
  2. Address major discrepancies in SOC projections from surface-soil estimates, and space-for-time experiments, with longitudinal deep carbon data collected by SOCnet.
  3. Position farmers to reach their soil health objectives, participate in market opportunities, and maintain ownership of the C sequestration narrative, by developing the tools needed to track, interpret, and document on-farm carbon stocks.

This work will help farmers realize new income opportunities and verify the climate mitigation potential of working lands.  


The Soil Organic Carbon Network (SOCnet) is a farmer-scientist collaboration monitoring long-term effects of farming practices on soil carbon (SOC) and other soil health metrics in the Upper Midwest. SOCnet is a network for accurately monitoring SOC change and helping farmers evaluate carbon-market opportunities. SOCnet links producer-driven on-farm research with long-term cropping systems experiments in Wisconsin, Iowa, and Minnesota, that serve as “hubs” for the network and play a critical role in our understanding of SOC change. On-farm sites complement long-term experiments providing essential information about how “real world” farming and environmental variation affect SOC dynamics.

Why SOCnet?

Many farming practices are promoted for their ability to improve soil health and sequester carbon (think cover crops, no-till, and manure addition). With commitments to carbon-neutral futures, both the private and public sectors are seeking ways to incentivize and reward farmers for carbon sequestration. But the “hype” around on-farm carbon sequestration is confusing and tends to look past contradictory scientific findings. It takes years to detect SOC change and long-term monitoring commitments and funding are difficult to secure. It is essential that we invest the time and rigor necessary to get these numbers “right”. Underestimating carbon sequestration means that farmers are not fully compensated for an important service to society. Overestimating carbon sequestration on the other hand exacerbates climate change, fuels extreme weather, and undermines food security.

Who is involved in SOCnet?

SOCnet is comprised of farmers from Iowa, Minnesota, and Wisconsin. Some are conducting on-farm experiments to evaluate the carbon sequestration potential of new practices on SOC stocks, while others are tracking well-established management practices on-farm. The scientific team includes faculty and staff at Iowa State University, the University of Minnesota, and the University of Wisconsin-Madison.


Click linked name(s) to expand/collapse or show everyone's info
  • Dr. Adam von Haden - Technical Advisor
  • Dr. Anna Cates - Technical Advisor
  • Dr. Gregg Johnson - Technical Advisor
  • Dr. Marshall McDaniel - Technical Advisor
  • Jamie Patton - Technical Advisor



H1: Soil organic carbon (SOC) dynamics (loss, stabilization, accrual) will vary within similar agronomic practices (e.g., cover crops) as a result of edaphic variability (soil mineralogy, climate).

H2: Soil organic carbon (SOC) accrual will increase along a gradient of soil health managment practices: annual interventions (e.g., cover crops) > diversification & inclusion of perennials > complete perennialization (e.g., conversion to pasture).  

H3: Deep carbon stocks (> 30 cm IPCC standard) will significantly impact carbon stock accounting and dynamics.

H4: On-farm experimental design (repeated vs. random sampling) & analytical approach (e.g., depth, mass) will have a significant impact on the interpretation of SOCnet results (to be evaluated using sensitivity analysis).  

Materials and methods:

SOCnet will consist of three research and engagement Tiers (Figure 2). This collaborative 3-Tiered framework integrates multi-location on-farm experiments with ongoing SOC monitoring and cropping systems research in Wisconsin (WICST), Iowa (Marsden Farm), and Minnesota (LTARN). WICST1 (Wisconsin Integrated Cropping Systems Trial) was established in 1990 and consists of cropping systems broadly representative of the North Central U.S. that include cash-grain, dairy-forage, grazing, and native grasslands. The Marsden Farm2 long-term experiment was established in 2001 and compares cropping systems of varying diversity including corn, soybean, small grains, and cover crops in Central Iowa. LTARN3 (the Long-Term Agricultural Research Network) is a network of three long-term experiments that were established across Minnesota in 2013 to evaluate cropping systems that represent a range of diversification strategies. Work at each long-term experiment has focused on understanding the productivity, profitability, and environmental benefits of alternative production strategies within cropping systems that are broadly reflective of regional practices. Each site employs a randomized complete block design, providing a robust statistical framework with which to evaluate the impact of agricultural management practices on SOC stocks. WICST, Marsden Farm, and LTARN (3 sites) will make up the SOCnet Tier 1 “hubs” (Figure 2, red).

Each Tier 1 hub will be linked to three Tier 2 on-farm locations (Figure 2, orange), creating the core layer of SOCnet. To expand the scope of study and increase our ability to scale our results across the region, we will prioritize Tier 2 sites with soils that differ significantly from the soils at the respective Tier 1 hubs. Each Tier 2 site will compare a “business-as-usual” treatment (BaU) representing typical on-farm practices with a farmer-defined “change in practice” (CiP) geared specifically for SOC accrual. Tier 2 locations will be selected so that on-farm cropping systems broadly align with those at the nearby long-term hub. An example of the broad cropping system categories at each Tier 1 hub are show in Table 1.

Table 1. Cropping system categories evaluated at each of the Tier 1 long-term hubs.

Cropping system categories

The Tier 1 hubs and Tier 2 on-farm sites will provide the foundation for meeting SOCnet objectives 1 and 2.

Over the initial 3-year grant cycle, we will expand the on-farm network to a third Tier (Figure 2, yellow), which will dovetail with ongoing regional soil health projects and on-farm networks tracking SOC like the extensive FFAR funded collaborative effort between our research team, the Soil Health Institute (SHI), and the Dairy Research Institute (DRI). Other collaborative networks associated with the three-state research team include Grassland 2.0 (SAS CAP, 2019-68012-29852), the cover crop research and outreach project (CCROP, WI), producer-led watershed groups (WI), Great River Greening (MN), Practical Farmers of Iowa (IA), and several recent or ongoing USDA HATCH (WIS03057), USDA CIG (NR183A750008G011) and SARE (LNC20-440) projects evaluating SOC stocks in paired on-farm settings associated with grazing of cool-season pastures and cover crops. We will solicit participation in Tier 3 with the help from the Tier 2 CFT and above-mentioned networks as well as through stakeholder meetings and field days. Tier 3 sites will be used to increase the diversity of soil types, climate, and management practices within SOCnet, thereby solidifying the anticipated outcomes for objectives 2 and 3 and maximizing the overall impact of SOCnet.

All soil sampling and processing will follow standard protocols. At the Tier 1 sites, sampling will occur in established research plots, with a minimum of two soil cores taken in random locations per plot per collection time. Soil sampling at the Tier 2 and Tier 3 fields will be based on the Terraton Experiment™ protocol as a guide to ensure a link with developing carbon market standards. In line with guidance from Terraton, Climate Action Reserve, and Verified Carbon Standard, Tier 2 and Tier 3 fields will be stratified into areas that are expected to contain relatively homogenous soils.4 Stratification will be based on the soil series given in the USDA NRCS Soil Survey Geographic Database (SSURGO), which integrates critical properties including slope, drainage classification, and soil texture. Two soil cores will be taken for each 5-acre area, with a minimum of one soil sample for strata smaller than 2.5 acres (see Figure 3). In fields larger than 20 acres, soil sampling will be restricted to a 20-acre area that is deemed to be representative of the entire field based on soil properties in the SSURGO database. This hybrid approach will allow for robust determination of SOC change while keeping to a manageable number of soil samples. The location of all soil samples will be georeferenced with a high precision GPS, and all future soil samples will be collected within 1 m of the original samples.

Soil Stratification

Most efforts to track changes in SOC focus on surface soils and ignore deeper SOC stocks, often for logistical reasons. However, changes in shallow SOC stocks (e.g., 0 to 30 cm) are not always related to changes in deeper SOC stocks, and losses at depth can offset gains in surface soils5. All soil samples collected for SOCnet will therefore include as much of the soil profile as possible while recognizing that shallow soils may occasionally limit sampling depth. Deep soil cores (0 to 100 cm) will be collected at Tier 2 and Tier 3 sites beginning in fall 2022 and fall 2023, respectively (Table 2). Deep soils collection at the Tier 1 sites will commence in 2024, as those sites have all recently collected deep cores during independent sampling campaigns. Re-sampling at all sites will occur at three-year intervals. Once collected, all cores will be stored at -4 °C until further processing can occur. Deep soil cores will be divided into four depth increments (0 to 15 cm, 15 to 30 cm, 30 to 60 cm, 60 to 100 cm). Field moist soil mass will be recorded, and a representative aliquot will be dried at 105 °C to determine total dry soil mass. The remaining sample will be sieved to 2 mm to remove gravel and plant debris, and the gravel-free dry weight will be used to calculate soil bulk density. A subsample of each soil sample will be dried, pulverized, and analyzed for total carbon (TC) and total N using flash combustion elemental analysis. Total soil organic carbon (SOC) will be directly measured on a subset of 10% of each site’s soil cores by acid fumigating an additional soil aliquot prior to elemental analysis6. If soil inorganic carbon (SIC) is detected by this method, additional soil cores from that site will be acid fumigated. If not, we will assume SOC is equal to TC. SOC stocks will be calculated by combining the SOC values with the gravel-free bulk density and SOC stocks will be presented in equivalent soil mass form to account for any changes in soil bulk density that could otherwise bias estimates of temporal SOC change7. Where present, SIC stocks and temporal changes will also be documented.

Table 2. Soil sampling details including sampling strategy, depth, and response variables for each of three Tiers.


sampling details

A suite of additional soil analyses will be performed to evaluate links between soil properties and SOC, elucidate the mechanisms underlying SOC change, and assess the temporal changes in SIC (Table 2). Soil texture analysis using the hydrometer method, and soil pH will be quantified in a 1:1 soil-to-water slurry (all Tiers). Agronomic nutrients (pH, OM%, P, K, Ca, Mg) will be quantified for the 0 to 15 cm depth using standard methods at a regional soil laboratory (Tiers 1 and 2). Particulate organic matter (POM) will be isolated from bulk 0 to 15 cm soils with a size-based fractionation scheme8, and organic carbon concentrations will be determined (Tiers 1 and 2). Mineral associate organic matter (MOAM) will be estimated as the difference between SOC and POM. Bulk dried samples will be archived for potential future analyses. All analyses less Agronomic nutrients will be conducted at the Jackson Lab (UW-Madison).

Crop yields from all plots and fields will be recorded, and residue return to soil will be estimated based on crop-specific harvest indices. All data will be curated by project personnel at the University of Wisconsin-Madison and stored redundantly in a shared cloud space. Data analysis will be overseen by Dr. von Haden working closely with Dr. Sanford and other members of the scientific team. Specific analyses will assess the response of SOC to climate, soil, and management factors as well as investigate the biological and physical mechanisms that may mediate the SOC response. Moreover, feedback between SOC change and yield response will be elucidated, as this relationship has significant economic implications.

Farmers will be invited to participate in the analytical processes, provided annually with updated data, and given complete access to the anonymized network database. The research team will help participating farmers quantitively track and interpret SOC changes in their fields. Researchers will also help farmers determine which land management practices are most effective at promoting SOC storage and whether differences in SOC storage rates varies across their fields. Farmers will be provided training in, and access to, decision support tools (DSTs) such as Smartscape™9 and Grazescape™. These two powerful decision support tools will allow farmers to evaluate how on-farm land management, including their selected CiP, will translate into a broad suite of environmental and economic outcomes. These economic outcomes not only include traditional crop revenue but also the value of ecosystem services such as SOC storage, reduced greenhouse gas emissions, and water quality improvements. Measurements of SOC change from all SOCnet sites will be used to enhance the underlying Smartscape™ and Grazescape™ biogeochemical model framework, which will in turn improve the accuracy and value of these tools.


  1. Wisconsin Integrated Cropping Systems Trial. University of Wisconsin-Madison.
  2. Marsden Long-Term Rotation Study. Iowa State University.
  3. Minnesota Long-Term Agricultural Research Network. University of Minnesota.
  4. Lawrence, P.G., et al. 2020. Guiding soil sampling strategies using classical and spatial statistics: A review.
  5. Sanford, G.R., et al. 2012. Soil carbon lost from Mollisols of the North Central U.S.A. with 20 years of agricultural best management practices.
  6. Harris, D., et al. 2001. Acid fumigation of soils to remove carbonates prior to total organic carbon or carbon-13 isotopic analysis.
  7. von Haden, A.C., et al. 2020. Soils’ dirty little secret: Depth-based comparisons can be inadequate for quantifying changes in soil organic carbon and other mineral soil properties.
  8. Poeplau, C., et al. 2018. Isolating organic carbon fractions with varying turnover rates in temperate agricultural soils – A comprehensive method comparison.
  9. Tayyebi, A., et al. 2016. SmartScape™: A web-based decision support system for assessing the tradeoffs among multiple ecosystem services under crop-change scenarios.
Research results and discussion:

Deep soil core processing and alaysis is currently underway.

  • Tier 2
    • soil sampling - completed fall 2022
    • soil processing - completed 2023
    • analysis  - partially completed, will be finished in March 2024
  • Tier 3
    • soil sampling - completed fall 2023
    • soil processing - in progress, anticipated completion June 2024
    • analysis - anticipated completion December 2024
  • Tier 4
    • soil sampling - planned for fall 2024
Research conclusions:


Participation Summary
26 Farmers participating in research


Educational approach:

The project seeks to "democratize" soil organic carbon and soil health data by building a farmer-scientist collaboration. In building the Soil Organic Carbon Network farmers and scientists are engaging in the co-development of on-farm experiments and decision support tools to assess, interpret, and maximize the real-world impact of robust, high quality soil organic carbon and soil health data. Farmers set goals and generate questions that they are keen to reach and answer on their farms. The scientific team then works to collect and interpret long-term, deep, and comprehensive soil organic carbon, soil health, and on-farm managmenet data from the broader network to facilitate on-farm decision making. Regular network meetings will also facilitate peer-to-peer learnign between participating farmers and guide future research directions. 

Project Activities

GROW Magazine: Can Farms Pull Carbon from Sky to Soil?
2023 OGRAIN conference: Crop rotations for a changing climate
Wallace Center: Soil Carbon 101
The Soil Health Collaborative: SOCnet
2023 North American Manure Expo - WICST and SOCnet
UW Organic Field Day: WICST and SOCnet
UMN Extention Podcast: Measuring and building soil carbon
Sucessful Farming: The truth about soil's ability to sequester carbon
Build Tier 2 farmer network - 9 farms (3 each in WI, MN, IA)
Build Tier 3 farmer network
Process and analyzes deep soil cores
Build SOCnet Database

Educational & Outreach Activities

9 Consultations
9 On-farm demonstrations
1 Published press articles, newsletters
4 Tours
10 Webinars / talks / presentations
5 Workshop field days

Participation Summary:

150 Farmers participated
20 Ag professionals participated
Education/outreach description:

There were several opportunities to engage with farmers and ag. professionals in 2023 and introduce them to the Soil Organic Carbon Network (SOCnet). These includeded: 1) establishing 9 on-farm experiments (3 each in WI, MN, and IA) as the core of SOCnet's Tier 2; 2) presenting at several invited webinars and conferences; 3) hosting multiple field days and tours at the Wisconsin Integrated Cropping Systems Trial (SOCnet Tier 1) in Arlington, WI; and 4) receiving some high-level media coverage. 

Project Outcomes

Key practices changed:
    2 Grants applied for that built upon this project
    30 New working collaborations
    Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.