CEFS Long-Term Systems Research: Providing the Building Blocks for Resilient Food Production Systems

Final report for LS15-267

Project Type: Research and Education
Funds awarded in 2015: $300,000.00
Projected End Date: 08/31/2019
Grant Recipient: North Carolina State University
Region: Southern
State: North Carolina
Principal Investigator:
Dr. S. Chris Reberg-Horton
North Carolina State University
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Project Information


The backbone of the FSRU will continue on: replicated plots of farming systems managed with farm-scale equipment.  Within that context, new research questions have emerged.  This research involves measuring outcomes never before measured or nesting new subplots within the experimental framework.  From the social sciences, we can ask how these systems interact with sustainability in the real world.  How do farmers weigh the choices in selecting farming practices from these various systems?  What factors play roles in farming practices that cannot be captured in an experimental protocol?  In this proposal, we have attracted researchers new to CEFS who have fresh ideas on relating this experiment to the sustainability issues of our time.  Most of these questions were never envisioned when the experiment was first designed.  From research on which farming systems emit the most greenhouse gases, to work on how land tenure affects the ability of farmers to adopt sustainable practices, the new research projects run the gamut of disciplines.

Project Objectives:

How systems impact long-term sustainability of soil and water resources,

system differences in resilience to perturbations in weather, inputs and market prices, and

how systems impact biodiversity, pest dynamics and ecological services of agriculture.

Long-term approaches that integrate the broad range of factors involved in agricultural systems are the focus of the Farming Systems Research Unit (FSRU).  The goal is to provide the empirical framework to address landscape-scale issues that impact long-run sustainability of North Carolina’s agriculture.  To this end, data collection and analyses include soil parameters (biological, chemical, and physical), pests and predators (weeds, insects, and disease), crop factors (growth, yield, and quality), economic factors, and energy issues.  Specific objectives for Phase II included:

  1. measuring greenhouse gas emissions from conventional and organic management systems using static chamber and continuous monitoring
  2. evaluating the social issues facing agricultural producers and landowners in adopting conservation agricultural systems on leased land
  3. testing novel weed seed destruction methods in conventional and organic systems
  4. investigating the impact of pasture termination method on soil organic carbon and nitrogen fractions with depth during subsequent cropping.


Click linked name(s) to expand
  • Dr. Wayne Robarge (Educator and Researcher)
  • Dr. Dara Bloom (Educator and Researcher)
  • Dr. Sarah Bowen (Educator and Researcher)
  • Dr. Wesley Everman (Researcher)
  • Dr. Alan Franzluebber (Researcher)
  • Dr. Shuijin Hu (Educator and Researcher)
  • Dr. Nancy Creamer (Researcher)
  • Dr. Michelle Schroeder-Moreno (Educator and Researcher)


Materials and methods:

The experimental design of the Farming Systems Research Unit (FSRU) trial is a randomized, block design with 14 treatments replicated three times for a total of 42 plots.  The same plot treatments are repeated continuously in time according to the designated rotation scheme.  The 14 treatments are sub-plots of the five overall treatments:

  1. CON (conventional cropping) – conventional tillage (CT)
  2. CON – no tillage (NT)
  3. ORG (organic cropping) – 3-yr crop/3-yr hay (A)
  4. ORG – Corn-Soy-Cover (B)
  5. ORG – Corn-Soy-Sunflower (conventional tillage) (C)
  6. ORG – Corn-Soy-Sunflower (reduced tillage) (D)
  7. ICL (integrated crop-livestock) – 3-yr hay/3-yr crops (1)
  8. ICL – 6-yr crops/6-yr pasture (2)
  9. ICL – 6-yr pasture/6-yr crops (3)
  10. FOR (managed forestry) – Ash (Ash)
  11. FOR – Bald cypress (Cyp)
  12. FOR – Longleaf pine (Pin)
  13. FOR – Black walnut (Wal)
  14. SUC – Old-field succession
Research results and discussion:

Several component-level research investigations have been published from this project, including:

  • Conducted a greenhouse experiment assessing the impact of corn roots and their associated mycorrhizal fungi on nitrifiers (ammonia-oxidizing archaea (AOA) and bacteria (AOB)) and soil N2O emissions in both organic and conventional soils, and found that mycorrhizal fungi significantly reduced N2O emissions, particularly in organically managed soils (Hu et al., unpublished)
  • Examined the impact of changes in C and N availability induced by elevated CO2 (Wu et al., 2017) and warming on soil denitrifier community and N2O emissions (Qiu, 2017)
  • Published a review of interviews from 30 fresh fruit and vegetable growers about their perceptions and motivations for selling produce to low-income consumers (Bloom et al., 2017)
  • Monitored N2O emissions following every rainfall event for three years (from early 2013 to later 2015), using the static chamber method (Knight, 2016)
  • Incubation experiments were carried out to quantify N2O and CO2 emissions from organic and conventional soils as influenced by different C and N availability (either cover crop incorporation or manure or urea additions) (Bloszies, 2016)

Research in conjunction with this project, but funded through other initiatives:

  • Soil collected from the Integrated Crop-Livestock System plots in 2015 for evaluation of soil biological activity in a greenhouse trial; study conducted by visiting scientist, Tangriani Simioni Assmann from the Technical University of Parana in Pato Branco, Parana, Brazil; manuscript in development
  • Soil sampled in transition phase from pasture to cropping in the Integrated Crop-Livestock System plots in 2016 for evaluation of soil bulk density, soil organic C and N fractions, nutrient concentrations, and soil biological activity; study conducted by Ph.D. sandwich student, Joao Bonetti from Federal University of Rio Grande do Sul in Porto Alegre, Brazil; oral presentation made at the Annual Meeting of the Soil Science Society of America in Phoenix AZ in November 2016; manuscript in development
  • As part of a series of wheat N timing and rate trials across North Carolina, two experiments were conducted in 2016/17 on no-tillage wheat following corn in the Integrated Crop-Livestock System plots; study conducted in collaboration with visiting Ph.D. sandwich student, Bernardo Borin from Federal University of Rio Grande do Sul in Porto Alegre, Brazil; manuscript in development
  • Reported on the positive impact of agroforestry design on reducing greenhouse gas emissions in agriculture (Franzluebbers et al., 2017) in a project funded by US-Forest Service and USDA-Agricultural Research Service
  • Reported on the lack of difference in soil health scoring functions between conventional and organic systems and between conventional and no tillage systems in the FSRU and other long-term studies in North Carolina (Roper et al., 2017)

Successes in our research efforts have been strongest in soil ecological evaluations focused on soil organic matter dynamics, microbial communities, and greenhouse gas emissions.  Our efforts will continue to provide greater clarity of how agricultural management affects soil ecological properties and processes.  Other successes have been achieved in assessing individual components of sustainable agricultural systems on various production and environmental quality aspects, such as the impacts of cover cropping on soil moisture and nutrient cycling and how livestock grazing and pasture management affect soil organic matter.

Challenges that our research team have encountered are overcoming spatial variability in soils from a floodplain environment, as well as ensuring continuity in research efforts with retirement of key faculty.  Regarding spatial variability, we have made strides to understand and predict how this will affect soil responses (Deiss et al., 2017).

Unexpected outcomes have been found with the significant emission of N2O from fungal species in soil (Mothapo et al, 2013; Chen et al., 2014).


Bloom D, Bowen S, Scott M. 2017. Bridging the gap: Examining small- and medium-scale farmers’ perceptions of selling to low-income consumers. Rural Advancement Foundation International, Pittsboro NC. 8 p. Accessed at: http://rafiusa.org/wp-content/uploads/2015/06/RAFI_Farmer_Interviews_Final_.pdf.

Bloszies SA. 2016. Soil microbial activity and organic carbon dynamics in low input agroecosystems. Ph.D. Dissertation. North Carolina State University.

Chen H, Mothapo NV, Shi W. 2014. The significant contribution of fungi to soil N2O production across diverse ecosystems. Applied Soil Ecology 73, 70-77.

Deiss L, Franzluebbers AJ, de Moraes A. 2017. Soil texture and organic carbon fractions predicted from near-infrared spectroscopy and geostatistics. Soil Science Society of America Journal 81, 1222-1224.

Dubeux J, Warren J, Franzluebbers A. 2016. Grazing cover crops in cropland. Southern Cover Crops Fact Sheet.

Franzluebbers AJ, Chappell JC, Shi W, Cubbage FW. 2017. Greenhouse gas emissions in an agroforestry system of the southeastern USA. Nutrient Cycling in Agroecosystems 108, 85-100.

Knight AM. 2016. Greenhouse gas emissions in long term agricultural production systems. Ph.D. Dissertation. North Carolina State University.

Macoon B, Daniel JB, Rogers J, Franzluebbers A. 2016. Introducing annuals in grazed pastures. Southern Cover Crops Fact Sheet.

Mothapo  NV, Chen H, Cubeta MA, Shi W. 2013. Nitrous oxide producing activity of diverse fungi from distinct agroecosystems. Soil Biology and Biochemistry 66, 94-101.

Mueller JP, Creamer NG, Barbercheck M, Bell M, Raczkowski C, Brownie C, Collins A, Fager K, Hu S, Jackson L, Koenning S, Kuminoff N, Linker M, Louws F, Mellage S, Monks D, Orr D, Seem J, Tu C, Wagger M, Walters R, Wossink A, Zhang W. 2006. Long-term, large-scale systems research directed toward agricultural sustainability. In: Raupp J et al. (Editors). Long term field experiments in organic farming. ISOFAR Scientific Series No 1. Berlin, Germany.

Roper WR, Osmond DL, Heitman JL, Wagger MG, Reberg-Horton SC. 2017. Soil health indicators do not differentiate agronomic management of North Carolina Soils. Soil Science Society of America Journal 81, 828-843.

Qiu Y. 2017. Soil microbial responses to climate change factors: Impacts on soil N2O emission and organic carbon decomposition. Ph.D. Dissertation. North Carolina State University.

Wu K, Chen D, Tu C, Qiu Y, Burkey KO, Reberg-Horton SC, Peng S, Hu S. 2017. CO2-induced alterations in plant nitrate utilization and root exudation stimulate N2O emissions. Soil Biology and Biochemistry 106, 9-17.

Participation Summary
105 Farmers participating in research

Educational & Outreach Activities

35 Consultations
12 Curricula, factsheets or educational tools
30 Journal articles
17 On-farm demonstrations
4 Online trainings
8 Published press articles, newsletters
5 Tours
7 Webinars / talks / presentations
8 Workshop field days

Participation Summary

750 Farmers
98 Ag professionals participated
Education/outreach description:
  • Engagement and collaboration of faculty, students, and staff has occurred repeatedly, including the following:

    We sought producer and stakeholder input into the research approach through field days and CEFS Advisory Board meetings:

    • Hosted a dozen CEFS interns for research experiences in each of 2016, 2017, and 2018
    • Hosted 15-20 sustainable agriculture workshops each year at CEFS
    • Cover crop plots established and tracked on 16 farms in North Carolina to examine cover crop impacts on soil moisture and nitrogen availability

Learning Outcomes

520 Farmers reported changes in knowledge, attitudes, skills and/or awareness as a result of their participation

Project Outcomes

Project outcomes:

Learning Outcomes

A project focused on characterizing greenhouse gas emissions from conventional and organic farming practices is highlighted here as an example of key learning outcomes. 

Nitrous oxide (N2O) fluxes from soil are considered a significant source of greenhouse gas emissions from land-based agricultural activities.  Nitrous oxide is ~300 times more potent a greenhouse gas as carbon dioxide (CO2).  Nitrogen availability in soil is a key factor in how much N2O emission might occur.  Nitrogen is often a key limiting factor in organic production systems due to the need for mineralization of organic compounds before becoming available for plant uptake.  Poor synchrony between release of organic N and the critical period of plant N uptake demand can lead to excessive N availability during some parts of the year, and therefore, potentially large fluxes of N2O loss to the atmosphere.  This study characterized N2O emissions between conventional and organic corn production systems using different methods of N2O flux detection. 

Soil N2O emissions have been and continue to be measured during the corn growing season in both (1) conventional, no-till management and (2) organic management systems using a combination of automated and static chambers.

Nitrous oxide fluxes are driven largely by rainfall events in coordination with N fertilizer applications (planting and side-dress).  However, in some instances there is emission with small rainfall events later in the growing season, as well as an apparent consistent background level of emissions.  These short term events are very transient in nature and dissipate before measurements with the static chambers would be possible unless teams were constantly on site.

To date, cumulative emissions estimated using static chambers and USDA-GRACEnet protocols appear to be underestimating N2O emissions by a substantial margin.  However, interpretation and obtaining quantitative measurements from the automated chambers over the larger areas we incorporate in our studies is still one of the primary objectives of our research.

We are now in contact and seeking further cooperation with researchers in Canada and Denmark who are also employing automated and static chambers in their efforts to quantify gas emissions from soils in various management systems.  A new faculty member, Dr. Alex Woodley who will be assuming responsibilities for continued measurements of N2O emissions in our group, has obtained funds to visit collaborators in Demark in the spring of 2020 to promote and further our cooperative effort.

We have been successful in establishing remote access to our data logging computer to be able to check the status of soil N2O fluxes with our automated system.  This has substantially improved the efficiency of our static chamber measurement efforts both in timing and intensity of an event.  The online system provides immediate feedback as well to other members of the group, e.g. who desire to soil sample after a major event to monitor soil microbial population dynamics.

We are actively building upon the base made possible by SARE funds to obtain other funding and expand our presence and measurement capabilities on site.  We have been able to double the number of automatic chambers we have, and we are now planning to enhance our instrument trailer on site to accommodate more equipment.  The continued support from SARE is critical to this effort providing a needed foundation to maximize use of other one-time funds.

We have hosted several groups at the site, including the Nature Conservancy, Environmental Defense Fund, Kellogg Foundation, and the Southern SARE Council.  In addition, classes from NC State’s agroecology program have toured the site to discuss N management in conventional and organic systems.  This funding has supported summer research assistants from NC State to work on this project, providing training and experience in agriculture and environmental research.

Project Outcomes

A project focused on organic grower perceptions is highlighted here as one of the key project outcomes.  Other more technical outcomes are being revealed in projects on soil health conditions and weed population dynamics of long-term farming practices, as well as greenhouse gas emission rates from conventional and organic farming practices.

A survey of organic growers in North Carolina led to improvement in our knowledge of the social constraints facing farmers.  A total of 18 farmers was interviewed.  All of the farmers were white men in the Piedmont and Coastal Plain regions.  They have all been certified organic at one point in time.  However, at the time of the interviews, only 15 out of 18 farmers were certified organic.  

Although all of the farmers grew organic grains, their primary farm products varied.  The reasons the farmers maintained organic certification were linked to personal values, better health of people and livestock, and the value-added benefit of marketing organic goods.  Many also cited how the higher prices on the organic market helped them to maintain production at a smaller scale.  Among those who dropped certification, sometimes the added value was not enough to offset the increased cost of labor and the frustrations of organic weed management.  One farmer viewed organic practices as less sustainable on his land (he preferred a no-till approach) and thought tilling soil for weed control was “excessive” and damaged soil health.  The certification process was manageable, but time-consuming for several farmers, but one mitigation strategy for this was to hire someone to handle all of the paperwork.

Although the grain farmers in this study did not cite land tenure as a reason for dropping or maintaining organic certification, they did note that leased land creates challenges related to decision-making on expensive infrastructure or land improvements such as drainage tiles, irrigation ponds, or land smoothing.  Without a long-term lease or landlord buy-in, these improvements did not seem worth it, and could even result in land-loss from other farmers outbidding them on rent for the more desirable, improved farmland.  Additionally, the ways in which farmers acquire and keep farmland revealed unexpected strategies, such as raising one’s own rent, renting land and not farming it, or putting family land in a conservation easement to resist development pressures in growing areas.  Several farmers were not concerned about maintaining their land leases, especially if they were not close to growing urban areas and felt trusting of their fellow community members to not “steal” the land from under them by outbidding the rent.

Farmer interviews revealed that growers are feeling some anxiety about leased land, and some are facing the reality of farming on fewer acres.  By employing organic as a strategy to make money on less land, farmers are able to maintain a livelihood.  However, concerns about losing leased land – either to the highest bidder or to development pressure – influenced decisions like raising their own rent, renting more land than they farmed, or holding off on infrastructure projects.

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.