Brief Summary of Minutes of Annual Meeting

The meeting was held virtually on August 21, 2023 after the summer board meeting of the Southern Cover Crop Council (SCCC). The meeting started with an introduction of all project participants. Dr. Nithya Rajan moderated the meeting. The discussions started with remarks from the NIFA representatives, Dr. Mathieu Ngouajio and Dr. Bisoondat Macoon. This was followed by objective report presentations. 

Dr. Jake Mowrer presented the report for Objective 1 [Identify a common set of biological and economic measures that can be applied across crop and cover crop combinations throughout the region to generate a region-wide database]. The Objective 1 team is looking at various soil health indicators and economic indicators of soil health. Activities to date include 1) forming the authorship team for the review paper that now has a full outline and a preliminary draft & 2) sources of funding for soil health research identified. Planned activities include pushing review manuscript forward and holding meetings for grant writing.

Dr. Audrey Gamble presented the report for Objective 2 [Select and evaluate summer and winter cover crop germplasm for regional adaptability and determine the appropriate timing of planting, seeding rates, utilization of cover crop goods (includes grazing), and termination to optimize benefits without adversely affecting cash crop cycles]. Dr. Gamble presented results from a legume species and seeding trial that was conducted in 2019-2020 and 2021-2022 with 10 states. Data analysis is ongoing. The team plans to submit a publication by January 2024. Key preliminary results include finding no systematic benefit of increasing the seeding rate of legumes (like previous small grain trials). Dr. Gamble also presented results from 2022-2023 cover crop variety trial.

Dr. Nithya Rajan presented the report for Objective 3 [Assess the influence of cover crops on soil moisture, nutrient cycling, and soil microbiology]. All members have ongoing experiments looking at various aspects of this objective, however, Dr. Rajan discussed the need to pursue grant funding to develop a common project including participants. Some of the research ideas that were proposed at the 2022 annual meeting are currently being researched by Dr. Rajan in cotton and Dr. Mulvaney in soybean. The team is planning to continue their efforts for grant proposal submissions and leveraging activities.

Dr. Carlene Chase presented the report for Objective 4 [Characterize cover crop efficacy for enhancing cropping system resilience to weeds, pests, and plant pathogens]. An update was provided for two studies. The first experiment includes 3 different cowpea lines x 5 seeding rates x 3 termination timing. The second experiment, funded by USDA_NIFA, aimed at finding delaying rye termination on biomass, weed suppression, and subsequent corn yield.

Dr. Mickie Swisher presented objective 5 report [Generate an economic database that researchers, technical advisors, and farmers can use to assess the short and long-term economic outcomes of cover crop use]. A review on the environmental impacts of cover crops was published. A manuscript is in preparation on factors that affect farmers’ adoption and intensity of cover cropping using the theory of planned behavior. This focuses on farmer perception towards climate change, sources of information and how they are perceived, demographic variables, farm characteristics, and how they interact to affect the adoption of cover crops. Feedback from think tanks and advisory councils from very experienced cover crop users include the following: 1) longer experiments are needed, especially for soil health; 2) larger scale is key as within-field variability can be large; and 3), not enough emphasis on profitability, too much on maximum yield. Several moved from very diverse mixtures to 3-4 species mixtures.

The meeting was wrapped up in the afternoon with a discussion about grant proposal writing. The meeting was adjourned at 2.30 PM.

Objective 1:

Soil health-specific funding has been sought as an objective team this year.  This includes solicitations from the Specialty Crop Research Initiative, Foundational and Applied Science Program, Conservation Innovation Grants, Sustainable Agricultural Systems, and others.  The objective team has not yet been awarded funding based on proposals. However, members of the objective team have been successful in securing awards.  Current efforts of the objective team include submitting proposals to the USDA-NIFA OREI and SAS programs for the FY 2024 cycle.

Objective 2:

Collaborators in ten states participated in a multi-state trial to evaluate winter legume cover crop species and seeding rates from 2019-2022. Overall, results from this trial illustrate the variation both among species and among varieties within species as well as highlight top-performing varieties for the Southern region. While these results draw from a wide range of environmental conditions representative of the Southern US, the cold-snap in December 2022 was unusual for this region. Results from brassica varieties and some more cold-sensitive clover varieties may not be representative of a more typical winter. Cereal rye, hairy vetch, and crimson clover varieties were among the top-performers for the 2022-2023 season. Although top-performing varieties of cereal rye and hairy vetch were generally the same across locations and termination timings, crimson clover varieties exhibited greater variation by location. Selecting a mix of top-performing varieties that offer complementary benefits, such as early season cover, biomass at termination, and nitrogen release after termination, can help maximum the benefits of cover crops to a succeeding cash crop system.

Objective 3:

The team continued to leverage ongoing research for this objective. There are a number of ongoing experiments in participating states where cover crops are being evaluated for its impact on soil moisture, nutrient cycling, and soil microbiology. Depending on the location and the type of cover crop used, varying responses were found. The team has several graduate students working on the projects related to Objective 3.  Team members are also actively seeking external grants to address goals related to Objective 3.

Objective 4:

Common Experiment 2 funded by USDA NIFA Sustainable Agricultural Systems Coordinated Agricultural Project award no. 2019-68012-29818 is in its third and final year of field research. The multistate study is focused on the effects of planting no-till corn into a rye cover crop (planting green) on weeds, insect pests, slugs, and pathogens. Although terminating rye after planting results in the higher cover crop biomass than termination 1-3 weeks before planting there was no difference in weed biomass at termination or at the V4-V5 stage of a subsequent corn crop. Compared to a no cover crop control all rye termination timings effectively suppressed weeds in the corn crop. However, post-planting rye termination resulted in a corn yield penalty compared with the control and the preplant termination timings. For a second multistate study aimed at developing seeding rate and termination timing recommendations for cowpea germplasm lines US-1136, US-1137, and US-1138 data analysis has been completed and a manuscript has been prepared that will be submitted for publication in 2024. 

Objective 5:

The team accomplishments in the current reporting period provide summative components in the research conducted over the life of this project. This work was itself built on previous research conducted by researchers who remain deeply involved in this final year of research under our current Hatch project. One team of social science researchers (Liu, Ruiz-Menjivar, Hu, Zavala and Swisher) completed a scientometric review of the existing literature about the environmental impacts of using cover crops (Knowledge Mapping of the Extant Literature on the Environmental Impacts of Using Cover Crops – A Scientometric Study, Environments 2022, 9(9), 120; https://doi.org/10.3390/environments9090120). This contribution to the literature will be used in the development of our on-going cover crop research. We conducted the final think tank meeting of experienced growers. This final discussion combined with our previous think tank meetings with cover crops users who have years of experience with cover crops combined with our field assessments of cover crop research plots each year provided us with three major conclusions based on farmers’ perspectives on the use of cover crops and provide the basis for future research.  (1) New adopters need to commit to a lengthy trial of cover crops on their farms to adequately assess both the biological and economic advantages of using cover crops. (2) Larger scale trials are needed to make direct comparisons between a farmer’s current practices to explore the full range of variance under field conditions. (3) Future research needs to focus on profitability, not maximum yield.  Farmers consistently find that the cost of materials and labor needed to maximize yield can reduce overall profitability. 

Boakye, D.A., P. Aryal, C. A. Chase, M.V. Bagavathiannan, A. Basche, H. Darby, M. L. Flessner, E. Haramoto, R.G. Leon, S.B. Mirsky, A. Robertson, M. Ruark, M.R. Ryan, N.J. Seiter, K. Tilmon, P. Tomlinson, J.F. Tooker, M. VanGessel, J.M. Wallace, J. Adam, T. Ferreira de Almeida, A. Decker, K. Loria, R. Matthiessen-Anderson, J.M. McVane, F.H. Oreja, D. Presley, A. Raudenbush, L. Ruhl, C. Sias, B. Scott, E. Sweep, and A. Waggoner et al. 2023. Effects of delaying rye cover crop termination on cover crop biomass, weed suppression, and corn yield. Proceedings of the Weed Science Society of America. https://wssa.net/wp-content/uploads/WSSA-WSWS-2023-Proceedings.html.

Boakye, D.A., C.A. Chase, D. Presley, S. Mirsky, A. Robertson, E. Haramoto, J. Tooker, R. Matthiesen-Anderson, A. Basche, M. Bagavathiannan, J.M. McVane, K. Loria, N. Seiter, J. Adam, J. Wavering, C. Sias, A. Waggoner, P. Tomlinson, M. Flessner, T. Ferreira de Almeida, J. Miller, M. VanGessel, H. Darby, M. Ryan, K. Tilmon, A. Raudenbush, V. Singh, M. Ruark, R. Leon, and L. Ruhl. 2023. Impact of rye cover crop termination timing on cover crop biomass, weed suppression and corn yield. American Society for Horticultural Science Annual Conference. https://ashs.confex.com/ashs/2023/meetingapp.cgi/Paper/40039.

Chase, C.A., D.A. Boakye, P. Aryal, N.T. Basinger, L. Fultz, A.V. Gamble, E. Haramoto, N. Rajan, V. Temu, and E. Valencia. 2023. Multistate assessment of cowpea cover crop germplasm, seeding rate, and termination timing effects on weed suppression. Proceedings of the Weed Science Society of America. https://wssa.net/wp-content/uploads/WSSA-WSWS-2023-Proceedings.html.

Liu, Y., Ruiz-Menjivar, J., Hu, Y., Zavala, M., & Swisher, M. E. (2022). Knowledge Mapping of the Extant Literature on the Environmental Impacts of Using Cover Crops—A Scientometric Study. Environments, 9(9), 120.