Compost for Carbon Sequestration on Irrigated Pasture

Progress report for OW20-358

OW20-358 (project overview)
Project Type: Professional + Producer
Funds awarded in 2020: $49,746.00
Projected End Date: 12/31/2023
Host Institution Award ID: G345-20-W7901
Grant Recipient: Colorado State University Extension
Region: Western
State: Colorado
Principal Investigator:
Retta Bruegger
Email
Colorado State University Extension
Co-Investigators:
Dr. Megan Machmuller
Email
Colorado State University
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Project Information

Summary:

Climate change threatens the viability of ranching and farming and poses impacts to society as a whole. Simultaneously, a disconnect between research and application by ranchers diminishes the ability of both to respond in an adaptive way. We propose to test a potential intervention for sequestering carbon, while integrating ranchers into the research process. Compost applications on rangelands and pasturelands may provide a win-win scenario for producers and society. Research indicated a 1-time application of compost increased soil organic matter content, enhanced plant growth, and contributed to climate change mitigation in California’s rangelands (Silver et al 2018). Though promising, these results are untested in western Colorado, an area with substantial soil and climatic differences from the locations of the original trials. Research and outreach will be integrated in this project. Producers and stakeholders will participate directly in research through iterative meetings where they will assist in interpretation of the data analyses and ultimately help develop recommendations based on the findings. The project outcomes include 1) recommendations in terms of the appropriateness of the practice for western Colorado pasturelands based on our findings, and 2) an engaged group of stakeholders who have direct experience participating in a scientific process.

Citations:

  1. Silver, W. L., Vergara, S. E., & Mayer, A. (2018). Carbon sequestration and greenhouse gas mitigation potential of composting and soil amendments on California’s rangelands. California Natural Resources Agency, 62.
Project Objectives:

Research Objectives

  1. Test the efficacy for western Colorado pastures of compost application using field trails, replication, and controls by 2023.
  2. Test the efficacy of a 1-time compost application to increase grass productivity.
  3. Test the efficacy of a 1-time compost application to sequester carbon and increase soil organic matter.
  4. Test the impact of a 1-time compost application on species composition.

Outreach Objectives

  1. Assemble a stakeholder group of producers and interested parties to advise, contribute and comment on research activities. Stakeholders will meet 3-5 times over the course of the project. We will meet 1) before the initial application of compost, 2) at the end of the first field season to assess how things went, and 3) after field results have been analyzed to interpret and discuss finding, and consider barriers and advantages to implementation, and develop recommendations.
  2. Present findings at the annual Delta Soil Health Conference (February each year in Delta, CO), Pasture Plot Field day (October every year in Hotchkiss, CO), and the Field Day at the Fruita Agricultural Experiment Station (summer/ fall).
  3. Compose article for the Small Acreage newsletter for fall 2023 (Circulation 6,000).
  4. Produce infographics and social media posts on the practice which we can post to our websites (https://rangemanagement.extension.colostate.edu/ and https://sam.extension.colostate.edu/ and other affiliates including Global Rangelands: https://globalrangelands.org/) and social media outlets (Facebook: @ColoradoStewardship and Instagram: coloradostewardship) by fall 2023.
Timeline:

Bruegger Compost WSARE Gantt Chart

Updated Project Timeline:

Bruegger Gantt Chart Revised 2022

Cooperators

Click linked name(s) to expand/collapse or show everyone's info
  • Lanny Denham - Producer
  • Mike Higuera - Producer
  • Cynthia Houseweart - Producer
  • Tom Kay - Producer
  • Lowell King - Producer
  • Ken Lipton - Producer
  • Steve Woodis - Producer

Research

Materials and methods:

Objectives 1-4

In order to complete our research objectives (Objective 1-4), we conducted the experiment at 2 sites in western Colorado. Sites are the Fruita Research Station (affiliated with CSU's Ag Experiment Station), and a producer's field near Ridgeway, CO.  We used a randomized complete block design that included 3 blocks consisting of 3 treatments each, 1. compost, 2. compost and fertilizer, 3. fertilizer only and 4. control. Plots were oriented in 10 by 360 foot strips and separated by at least 10 foot buffers, aligned parallel to the direction of the flow of water in the field. There were 12 plots total at each site (4 treatments x 3 blocks per site x 2 sites = 24 treatment plots) applied in the spring of 2021. We were delayed in starting due to the COVID-19 pandemic, but tested compost in 2020, and applied treatments in 2021. In the spring of 2022, we split the Fruita plots in half and applied fertilizer to plots previously treated with compost, fertilizer, and compost+fertilizer (no fertilizer applied to the controls). This enabled us to contrast outcomes of compost on plots that were treated differently after compost application. We collected soils data in spring 2022 and in April 2023. In each plot, we used a Giddings probe to create an aggregate sample of 3 profiles per plots. Profiles were aggregated by plot at 4 depths: 0-10 cm, 10-30 cm, 30-50 cm, and 50-100 cm (Ryals et al 2014, Silver et al. 2018). We tested soil samples and measure total carbon/nitrogen stocks, soil texture, and soil health metrics. Soil health metrics included: 

  • Carbon (TC, SIC, SOC)
  • Nitrogen (NH4, NO3, TON)
  • Phosphorus (Olsen P)
  • POX-C (proxy for microbial/active carbon)
  • Water holding capacity
  • Beta-glucosidase (Microbial extracellular enzyme)
  • PH
  • Soil Respiration
  • Water Stable Aggregates
  • CEC (Cation Exchange Capacity)
  • Salts

At each plot, we also sampled above-ground biomass production using the clip-and-weigh method (Coulloudon et al 1998) before each hay cutting in 2021 and 2022. Samples were dried at 120 degrees for 72 hours, and then weighted. We sampled vegetation composition in 2021 and 2023 using the line point intercept method (Herrick et al. 2005) to contrast before and after species composition. 

We analyzed all variables, including yield/ production, total carbon/nitrogen stocks, inorganic nitrogen, plant biomass production and plant species composition across treatments using a linear mixed-model in R and JMP. 

Objective 5

An innovative part of this grant was the involvement of the stakeholder group in developing recommendations based on the research findings (Objective 5).  The ‘stakeholder group’ consisted of involved ranchers, Extension agents, and interested parties from the Natural Resources Conservation Service and Conservation Districts. We planned that this group would assemble 3-5 times over the course of the experiment to make decisions, provide feedback and evaluate progress. In total we met 4 times to decide on what compost to use, what to test, what fields to use, interpret first year results in 2022, and interpret final results in 2023 (described below). 

We hosted a final stakeholder meeting in December 2023. We asked the the group to assist us in interpreting the results of the analyses and developing recommendations for practice, per the original outreach objectives. R. Bruegger has facilitated several groups doing citizen and participatory science (Bruegger et al. 2016). We employed methods of structuring conversations detailed in Bruegger et al. and elsewhere to enhance discussion. We asked each member to individually reflect in response to prompts such as “I observe…..”, “I am surprised by…”, “I think the results mean…because………” etc. We then used these responses as the basis of a conversation to further interpret results, and ultimately integrated feedback into recommendations based on the findings. Producers play a critical role in evaluating the risks and benefits of adopting a new practice and are ultimately the ones managing land. On this project, they provided meaningful feedback at various junctures. These included, what compost to use, what to consider when selecting the compost, how to set up the field trial, and feedback on the results. 

For our outreach objectives (Objectives 4-6), the methods are described below under “Educational Outreach Activities and Materials.”

Citations: 

  1. Bruegger, R. A., Fernandez-Gimenez, M. E., Tipton, C. Y., Timmer, J. M., & Aldridge, C. L. (2016). Multistakeholder development of state-and-transition models: a case study from northwestern Colorado. Rangelands, 38(6), 336-341.
  2. Coulloudon, B., Eshelman, K., Gianola, J., Habich, N., Hughes, L., Johnson, C., ... & Willoughby, J. (1999). Utilization studies and residual measurements. UD o. Interior, editor. BLM Technical Reference, Washington, DC.
  3. Herrick, J. E. (2005). Monitoring manual for grassland, shrubland and savanna ecosystems.
  4. Ryals, R., Kaiser, M., Torn, M. S., Berhe, A. A., & Silver, W. L. (2014). Impacts of organic matter amendments on carbon and nitrogen dynamics in grassland soils. Soil Biology and Biochemistry, 68, 52-61.
  5. Silver, W. L., Vergara, S. E., & Mayer, A. (2018). Carbon sequestration and greenhouse gas mitigation potential of composting and soil amendments on California’s rangelands. California Natural Resources Agency, 62.
Research results and discussion:

Our Results

Pasture Yield

  • Compost plots were less productive (p = 0.008; 1,585 lbs/acre +458) compared to fertilized plots and were not different than controls (i.e., untreated) in Year 1.
  • However, any negative effect from compost was not apparent in year 2 (no differences among plots treated differently in year 1 in year 2).
  • Plots where fertilizer was applied in year 2 were significantly more productive than non fertilized plots (p = 0.001745), but there was no difference among treatments from year 1.

Soil Organic Carbon & Soil Health

  • A 1-time application of compost did not increase SOC Stocks. There were no difference among treatments at any horizon sampled.
  • No treatment effects on total nitrogen stocks.
  • Despite high application rates, compost did not increase soil salinity. 
  • There were no treatment differences among treatments in soil health metrics analyzed. 

Species composition

  • There were no differences among treatments in the proportion of exotic species pre and post treatment.

Other Studies

  • When compared with other studies, compost on irrigated pasture and rangeland has mixed results. A 2023 synthesis (Kutos et al. 2023) reviewed studies on rangeland and found that in 15 out of 37 studies, compost did not lead to an increase in Soil Organic Carbon compared to the control. In 22 out of the 37 studies, compost did lead to an increase in Soil Organic Carbon compared to the control. In terms of production, the same review yield was not different in compost versus control in 50% of studies (Kutos et al. 2023). More locally,  2 studies from the Northern Colorado Front Range showed conflicting results on irrigated pasture (one study found an increase in SOC and the other found no increase - Mclelland et al. 2022 and Mikha et al. 2017). Given these results, our study was not anomalous. These results and the results of our study suggests that compost may not always lead to intended results of increasing SOC or production, but understanding when and where it does would provide value to producers wanting to adopt this practice.

Citations: 

  1. Kutos, S., Stricker, E., Cooper, A., Ryals, R., Creque, J., Machmuller, M., ... & Silver, W. L. (2023). Compost amendment to enhance carbon sequestration in rangelands. Journal of Soil and Water Conservation, 78(2), 163-177.
  2. McClelland, S. C., Cotrufo, M. F., Haddix, M. L., Paustian, K., & Schipanski, M. E. (2022). Infrequent compost applications increased plant productivity and soil organic carbon in irrigated pasture but not degraded rangeland. Agriculture, Ecosystems & Environment, 333, 107969.
  3. Mikha, M. M., Widiastuti, D. P., Hurisso, T. T., Brummer, J. E., & Davis, J. G. (2017). Influence of composted dairy manure and perennial forage on soil carbon and nitrogen fractions during transition into organic management. Agriculture, 7(5), 37.
Participation Summary
9 Producers participating in research

Research Outcomes

Recommendations for sustainable agricultural production and future research:
  • Given that results on composts' efficacy are mixed in terms of yield and SOC, there is risk involved in this practice as the costs are significant and may not produce intended results. If compost is the right choice for an operation depends on context of an operation, including crop N demands, dominant vegetation type if irrigated pasture or rangeland - i.e., annuals or perennial grassland), presumed mineralization rates, etc., and that operations unique goals (i.e., if they are willing to risk reduced yields in order to reduce reliance on synthetic fertilizers, or for other goals).  
  • In irrigated pastures, the risk of invasives due to compost is presumably low since typical management involves nutrient additions and weed management. There was no increase in invasive species due to treatments in our study. 
  • In order to maximize the potential benefits and reduce risk, we recommend timing of application relative to crop use so N in compost has time to mineralize before that crop needs the N. We also recommend some kind of incorporation, such as harrowing, in irrigated pasture to reduce losses. 
  • Compost amounts should be calibrated to N requirements of the crop and presumed mineralization rates. 
2 New working collaborations

Education and Outreach

40 Consultations
3 Curricula, factsheets or educational tools
1 On-farm demonstrations
2 Published press articles, newsletters
2 Webinars / talks / presentations
6 Workshop field days
1 Other educational activities: Social media distribution

Participation Summary:

40 Farmers participated
55 Ag professionals participated
Education and outreach methods and analyses:

Consultations - 40

We consulted with farmers and ranchers, and others, via regular updates, meeting invitations, incidental interactions, and phone calls to coordinate the implementation of the experiment on local ranches. 

Curricula, factsheets or educational tools - 11

  1. 1 Fact Sheet (draft as of of 2/28 pending review 2024 V2 Fact Sheet Draft)
  2. Write up for Board of Governors SARE Compost write up for BOG Concise
  3. 1 Project summary for Field Tour CompostTalkingPointsCSCB 6-21
  4. 1 webpage 
  5. Stakeholder group communications:
    1. June 2020: A scope of work covering the timeline, commitment and goals of the project. This was a reiteration of the submitted proposal, but served to remind people of the experiment, and invite people to participate.
    2. Compost Data Handout (Fall 2020). Stakeholder report on compost quality to inform decision-making on which compost to apply after sampling 4 large, industrial composters in the Montrose/Delta/Mesa County area for salts, nitrogen and other nutrients and chemical characteristics. 
    3. 2.26.2021 Compost Stakeholder write-up (March 2021)A second education tool to the involved producers on the project, which was a summary of the work we've done so far, and explanation of how we integrated their feedback (gathered at meetings) and built upon it to move forward with the project. it also summarized the decisions made so far, and the timeline on the experiment. 
  6. Social media post at ColoradoRangelands; 922 followers.
  7. 5/15/2023 Post to the CSU Extension Events list-serve, reaching 763 producers in the local 4 county area on final experiment results and promoting the webpage.
  8. 2/5/2024 Post to the CSU Extension Events list-serve, reaching 763 producers in the local 4 county area on final experiment results and promoting the webpage.

Workshop / field days - 6

2020-2021

Given the COVID-19 pandemic, we were not able to meet in person, but we did host 2 virtual meetings with stakeholders, the first in June 2020, and the second in September 2020 to discuss and get their input in to the experiment. These meetings were attended by those who wrote support letters for the project, and a few other interested parties. At the initial meeting in June 2020, critical discussions were around 1) compost quality, and 2) locations of plots. Based on this input, we undertook testing of compost, and we also changed one plot location so the pasture would be more representative of regional practices.  In March 2021, we joined an outdoor meeting of farmers/ ranchers in the Delta County area who were interested in composting. We have no results from the experiment yet, but we were able to connect with other producers interested in compost application.

Meeting slides are below:

In July of 2021, we hosted an Ag Field day in collaboration with the Colorado Department of Agriculture. We did not have results from the project, but they were interested in visiting the plot and learning about the experiment. 

2022

We hosted a webinar meeting for stakeholders involved in the project to give us feedback and for them to learn about work that's been done. 

2023

  • We corresponded with producers to update them on progress.
  • We hosted a wrap-up meeting in December 2023 to get input on recommendations using the findings.
  • We used the WSARE Survey to assess learning/ outcomes
  • Presentation 2023.12.14 WSARE Compost Update

2024*

*Technically after project is over but we finished the outreach objectives this year

Education and outreach results:

Our outreach objectives and corresponding achievements are listed below. 

  1. Objective: Assemble a stakeholder group of producers and interested parties to advise, contribute and comment on research activities. Stakeholders will meet 3-5 times over the course of the project. We will meet 1) before the initial application of compost, 2) at the end of the first field season to assess how things went, and 3) after field results have been analyzed to interpret and discuss finding, and consider barriers and advantages to implementation, and develop recommendations.
    1. Achievements: We had a total of 4 meetings from 2020-2023, and stakeholder retention was high in these meetings across the 3 years of this project. Stakeholder feedback was incorporated throughout the study, and into the final products. For example, stakeholders helped give criteria for the type of compost we used and select the compost. Their input at the end helped our interpretation of the results and context. This was an effective way to meaningfully engage a group of 'early adopters' in the experiment and results. 
  2. Objective: Present findings at the annual Delta Soil Health Conference (February each year in Delta, CO), Pasture Plot Field day (October every year in Hotchkiss, CO), and the Field Day at the Fruita Agricultural Experiment Station (summer/ fall).
    1. Achievements:
      1. We presented finding to 50-60 producers and ag-adjacent individuals at the 2024 Food and Farm Forum/ Soil Health Conference. In recent years, the Delta Soil Health Conference merged with the Food and Farm Forum. This venue is a great venue for reaching individuals who are interested in sustainable practices, and compost in particular. 
      2. We held 1 on-site field day in conjunction with the Colorado Department of Agriculture in 2021.
      3. We are scheduled for the fall 2024 Fruita Agricultural Experiment Station tour. 
  3. Objective: Compose article for the Small Acreage newsletter for fall 2023.
    1. Achievements: In order to achieve more consistent access for the public, we decided on making a fact sheet, a central landing website, and using our local newsletter to fulfill the above objective. Once the draft fact sheet is finalized, we will link it to our webpage. This creates easier access for stakeholders on the CSU Extension Range Management webpage.  Specifically,
      1. Due to staff turnover, the Small Acreage Newsletter was no longer an option. Instead, we sent out 2 updates via our newsletter in 2023 and 2024. The list-serve goes to 763 producers and ag-adjacent individuals in our 4 county area. 
      2. We also have produced a draft fact sheet , which will be finalized pending reviewer feedback, and distrusted via the webpage, social media and newsletters. 
      3. Finally, we created a webpage. A webpage provides a central landing page for the public to access. It is also easier for us to update periodically. With the webpage, we are able to update information and then use various channels to promote the webpage as new content is added. Traffic on the website varies but ranges from 8,817-11,400 hits/year. 
  4. Objective: Produce infographics and social media posts on the practice which we can post to our websites (https://rangemanagement.extension.colostate.edu/ and https://sam.extension.colostate.edu/ and other affiliates including Global Rangelands: https://globalrangelands.org/) and social media outlets (Facebook: @ColoradoStewardship and Instagram: coloradostewardship) by fall 2023.
    1. Achievements: We created this social media post/infographic posted at @RangelandsColorado. See above description of the webpage (or see https://rangemanagement.extension.colostate.edu/compost/). Due to staff turnover, @ColoradoStewardship and https://sam.extension.colostate.edu/ are no longer under my purview. Instead, we used @RangelandsColorado (started in 2020 in response to the need for more online venues for outreach during the shut-down) which has 922 followers, and during periods of high activity,  a reach of 30,000. The website https://rangemanagement.extension.colostate.edu/ is still under my purview, and we created a page there (described above). Though a deviation from the original venues for this outreach objective, we feel that these alternate social media and listserv outlets achieve the intent of the original objective, and are more current and used sites that our stakeholders access. 
9 Farmers intend/plan to change their practice(s)

Education and Outreach Outcomes

Recommendations for education and outreach:

Based on our outreach objectives, we recommend that those seeking to disseminate results customize methods of dissemination based on the audience, and their interest level/ capacity in the project. We found value in having a highly engaged stakeholder group in this project. These individuals came to several meetings over the 3 years of this project, and we created frequent opportunities for contact and involvement. This level of engagement was important for us, because it helped shaped the project and ensured that the project goals were aligned with real-world questions and concerns. However, the trade-off is that it reached fewer individuals. Not everyone wants to or can be this engaged. Thus, we recommend that projects produce outreach products and share results in venues that that are catered to audiences that need information in quicker and more efficient formats. For example in our project, these took the form of our website, sending out summaries in our 700+ person list-serve, public lectures, and field days. We also sought conference venues that would attract individuals interested in this practice. In order to disseminate results effectively, a one-size-fits-all approach does not work, and instead we recommend customizing outreach products and efforts to varying levels of engagement to both reach "early adopters" and those who typical adopt later, or other busy agricultural professionals. 

While we used the WSARE Evaluation Survey at producer meetings and at the Food Farm Forum/Soil Health presentations, we did not always get the best response. Thus, it is difficult to judge behavior change from those who opted not to take the survey, or those who visited the website or social media, or received the newsletter. Nonetheless, numbers from people who did return surveys are reported below. 

12 Producers reported gaining knowledge, attitude, skills and/or awareness as a result of the project
Non-producer stakeholders reported changes in knowledge, attitudes, skills and/or awareness as a result of project outreach
30 General public
20 Ag Service Providers
Key changes:

  • Improved my awareness of the topics covered -25

  • Provided new knowledge -23

  • Provided new skills - 10

  • Modified my opinions or attitudes - 15

  • Adopt one or more of the practices shown - 11

  • Increase the operation’s diversifications - 10

  • Reduce my use of purchased off-farm inputs - 8

  • Incorporate value-added into some aspect of my operation -8

  • Increase my networking with other producers - 10

  • In the next year I am likely to use some aspect of this project in an education program that I plan or participate in -10

  • In the next year I am likely to use some aspect of this project as a resource I will make available to producers -17

  • In the next year I am likely to use some aspect of this project as a professional development tool for my peers
    13

  • In the next year I am likely to use some aspect of this project improve advice/counsel I give to producers -17

Information Products

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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.