Cover Crops and Cropping System Sustainability in a Changing Global Climate

Progress report for LS20-335

Project Type: Research and Education
Funds awarded in 2020: $299,995.00
Projected End Date: 03/31/2023
Grant Recipients: Middle Tennessee State University; University of Kentucky; Auburn University
Region: Southern
State: Tennessee
Principal Investigator:
Dr. Samuel Haruna
Middle Tennessee State University
Co-Investigators:
Dr. Song Cui
Middle Tennessee State University
Dr. Audrey Gamble
Auburn University
Dr. Seockmo Ku
Middle Tennessee State University
Dr. Chaney Mosley
Middle Tennessee State University
Dr. Edwin Ritchey
University of Kentucky
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Project Information

Abstract:

Improving crop productivity and cropping systems resilience in a changing global climate is a big challenge for governments, scientists and producers around the world. The challenge is exacerbated, due to the predicted 17% human population increase and 0.7 – 1.8°C temperature increase by 2050. Rising temperatures may affect the soil ecosystem services, crop productivity and agricultural and environmental sustainability. Therefore, it is important to identify soil and crop management practices that are more adaptive to a changing climate. The adoption of cover crops has been encouraged, through various agricultural policies, due to their benefits in enhancing soil quality and health, crop productivity and environmental sustainability. The goal of this project is to evaluate the influence of cover crops on in situ soil thermal properties and how these may influence crop productivity and agricultural resilience in a changing climate. Both the TP01 thermal sensors and HFP01 heat flux plates were installed in plots planted to cover crops and plots with no cover crops on two farmer fields in Middle Tennessee for in situ measurement of Thermal conductivity and heat capacity. Soil temperature and water content sensors were also installed on these fields after cover crops were planted. Soil samples were collected from each field right after cover crops were planted for the baseline analysis of soil bulk density, water retention, saturated hydraulic conductivity, pore size distribution, soil nitrate, organic carbon, soil pH and microbial biomass. A week before the termination of cover crops, soil samples were also collected and analyzed for the aforementioned properties. Results showed that volumetric heat capacity was 13% higher under cover crop, compared with no cover crop management. As a result of higher bulk density, no cover crop management had 21% higher thermal conductivity, and 35% higher thermal diffusivity compared with cover crop management. This suggests that cover crops may be able to resist extreme soil temperature changes and this could lead to improved soil health and crop productivity under this cropping system. Water infiltration measurements were also made just prior to cover crop termination (during April) and again two months after termination (during June). Results showed that cumulative infiltration after 2 hrs was 52% higher in April and 68% higher in June under cover crop compared with no cover crop management. Further, in situ measured saturated hydraulic conductivity was numerically higher under cover crop compared with no cover crop management. These results show that cover crops can reduce surface runoff and soil loss while increasing water infiltration and storage, and this can improve crop productivity. Research efforts have resulted in 2 published manuscripts, and 1 manuscript in production. Nine undergraduate students were involved during the second year as undergraduate research assistants. Seven of those students are also co-authors on one of the manuscripts that resulted from this research. Outreach activities were carried out in Tennessee and Kentucky during the second year. In Tennessee, over 500 high school students participated in a day-long activity which introduced them to the various aspects of this research, including the benefits of cover crops. In Kentucky, several education efforts were included in several extension publications that have been made available to over 200 recipients. During the third year, we plan to hold several outreach activities in Tennessee, Kentucky, and Alabama. We will also conduct further research on crop yield, in situ water content under cover crop management, and soil hydraulic properties. Results will be published in scientific journals.

Project Objectives:
  1. Investigate the interaction between cover crops and soil health indicators (bulk density, soil pH, soil organic carbon, soil water content, soil water infiltration) on in situ measured soil thermal properties (thermal conductivity, volume-specific heat capacity, thermal diffusivity) (farmers will be involved with sensor installation and soil sample collection). Learning Outcome: participating farmers learn the philosophies behind soil sample collection for scientific and agronomic purposes and the mechanisms through which cover crops may help buffer against extreme soil temperature change. Action Outcome: Growers increase cover crop use to improve soil health and buffer against extreme soil temperature change,
  2. Assess the role of cover crops and in situ measured soil thermal properties on microbial (gram (+) bacteria, gram (-) bacteria, arbuscular mycorrhizae, actinomycetes, rhizobia, and protozoa) population and activity and on greenhouse gas (CO2, CH4, N2O) emissions with the help of farmers. Learning Outcome: 7 researchers, farmers and educators learn to optimize microbial activity and reduce greenhouse gas emissions through cover crop usage. Action Outcome: Researchers and educators develop guidelines on incorporating cover crops for reduced greenhouse gas emissions,
  3. Evaluate the interaction between cover crops, soil thermal properties, microbial activity and crop yield (farmers will be trained on the use of UAS for yield monitoring). Learning Outcome: 20 farmers learn to use UAS for crop yield monitoring. Action Outcome: 10 farmers integrate technology for yield monitoring.
  4. Educate local producers on benefits of using cover crops to improve productivity and enhance cropping systems resilience. Disseminate research findings, with farmer input, through training and extension services. Learning outcome: 60 farmers in 3 states (Tennessee, Alabama, and Kentucky) learn to improve crop productivity through proper management of cover crops. Action Outcome: Educators organize farmer-led field days and distribute recommendations on climate-conscious cover cropping for improved productivity and environmental resilience.

Cooperators

Click linked name(s) to expand/collapse or show everyone's info
  • Adam Daugherty - Technical Advisor (Educator)
  • Adam Daugherty - Technical Advisor (Educator)
  • Chris Hancock - Technical Advisor (Educator)
  • Chris Hancock - Technical Advisor (Educator)
  • Will Hutchinson - Producer
  • Sammy Morton - Producer
  • Jackie Reed - Technical Advisor (Educator)
  • Jackie Reed - Technical Advisor (Educator)
  • Jamie Weaver - Producer

Research

Materials and methods:

The research fields are located in Rutherford County and Coffee County, both in Tennessee. The fields are laid out in a randomized complete block design with two treatments (cover crop vs. no cover crop) and three replicates of each. 

Both fields are classified as Fragiudults with particle size analysis currently underway to determine the exact soil texture on both fields. During November-December 2020, soil samples were collected from each plot at 6 cm depth increments from the soil surface down to a depth of 30 cm to determine baseline soil physical and hydraulic properties. These properties included soil bulk density (core method), saturated hydraulic conductivity (constant and falling head methods), water retention (at 0, -0.4, -1.0, -2.5, -5.0, -10.0, -20.0, -33.0, -100.0, -300.0, and -1500.0 kPa soil water matric potentials using pressure plate apparatus), thermal properties (thermal conductivity, heat capacity, and thermal diffusivity using a KD2 Pro in the laboratory) at the various soil water potentials, and pore size distributions (using the capillary rise equation from soil water retention data). Additional soil samples were collected from the aforementioned soil depths for the determination of baseline microbial community structure using the phospholipids fatty acid analysis. In addition, just before the cover crops were terminated in 2021, soil samples were collected and analyzed for the aforementioned properties to enable researchers, farmer cooperators and students assess the influence of cover crops on these properties. Water infiltration measurements were also made using a double ring infiltrometer just prior to cover crop termination and 2 months after their termination to understand the effects of cover crops on in situ measured water infiltration during the cash crop growing season.

Further, during November and December 2020, The TP01 thermal properties sensors and HFP01 heat flux sensors were buried in each field at 5 cm depth and connected to data loggers. The sensors are able to take measurements every 6 hours and the dataloggers average these measurements over a 24-hour period to generate an average daily in situ soil thermal property measurement. In addition, three watermark sensors were buried in each plot at 0-10, 10-20, and 20-30 cm depths. Soil temperature sensors were also buried at these depths. Both sensor types take water energy and temperature measurements every hour. These sensors are linked in a mesh at each location and connected to the internet through cellular gateway. The watermark sensor measures soil water energy (rather than soil water content) and the choice of these sensors adds uniqueness to the data being generated (most literature report on water content). However, if needed, soil water content can be calculated from these measurements using the van Genuchten equation and soil water characteristics curve.

Other measurements that will be collected in the future include cash crop yield data. Yield data will be collected after the cover crops have been terminated and the cash crops planted. They will be collected throughout the growing season. Crop yield and vigor, at various stages of crop growth will be measured using a vegetation index derived from UAS imagery. This will also provide a learning opportunity for collaborating farmers. We are also currently measuring greenhouse gas emissions from the field using the Gasmet DX4040 portable gas analyzer. Two farmers and 9 undergraduate students participated in this effort.

Research results and discussion:

Laboratory measured soil thermal properties results showed that while soil properties (bulk density, soil organic carbon, thermal conductivity, volumetric heat capacity, and thermal diffusivity) were similar between cover crop and no cover crop management just before cover crops were planted, these properties were significantly different prior to cover crop termination. For example, bulk density was 18% higher under no cover crop management compared with cover crop management prior to cover crop termination. This was attributed to the roots of cover crops opening up soil pores and also due to the higher soil organic carbon under cover crop management (organic carbon was 14% higher under cover crop compared with no cover crop management). Therefore, no cover crop management significantly increases thermal conductivity and thermal diffusivity. Further, as a result of higher soil organic carbon and water content, volumetric heat capacity was 21% and 14% higher at saturation and field capacity under cover crop compared with no cover crop management. This demonstrated that, under laboratory conditions, cover crop management can buffer against significant heat transfer within the soil, helping to keep the soil temperature stable for longer periods. In a changing global climate, cover crops can provide a more conducive environment for microbial activity, nutrient transport and availability, and potentially increased crop productivity compared with no cover crop management. The result of this study has been published in Soil Research journal and it is attached with this report.

In situ measured soil water infiltration result showed that cumulative water infiltration was 52% higher prior to cover crop termination and 68% higher 2 months later under cover crop compared with no cover crop management. Since soil water is the most limiting crop productivity factor, cover crops has the potential to improve crop productivity significantly by increasing soil water infiltration, and this can persist for up to 2 months after their termination. Further, the Green-Ampt and Parlange model estimated sorptivity parameter, which quantifies the influence of capillarity on liquid movement into the soil, was numerically higher under cover crop compared with no cover crop. This indicates that cover crops can transpire excessive water out of the field during very wet growing seasons. This can be beneficial in an increasingly variable atmospheric climatic condition. In situ measured saturated hydraulic conductivity results showed that cover crops can significantly increase ground water recharge compared with no cover crop management. This enhances the ability of cover crops to reduce surface runoff of sediments and soil nutrients. This study has been fully published in Soil Science Society of America Journal and is attached with this report.     

Soil hydraulic properties were analyzed just prior to termination, and again monthly during May, June, and July to understand the influence of cover crops during the cash crop growing season. Results showed that soil bulk density was 23%, 12%, 11% and 10% lower under cover crops compared with no cover crop management during April – July, respectively. This suggests that cover crop residues can reduce the kinetic energy of raindrops which leads to less raindrop-induced soil consolidation and possibly soil detachment. Four months after cover crop termination in July, total porosity was 50% higher under cover crop management compared with no cover crop management. As a result, laboratory measured saturated hydraulic conductivity during July was two times higher under cover crops compared with no cover crop management. Further, cover crop plots had 64% higher volumetric water content at saturation compared with no cover crop management during July. This demonstrates that cover crops can increase crop productivity by significantly increasing soil water storage. This study has been fully published in Soil Use and Management journal and a copy is attached with this report.

During the third year, we will collect more soil samples and continue to analyze our results and we hope to have some manuscripts ready for peer-review in the coming months.

Participation Summary
3 Farmers participating in research

Educational & Outreach Activities

2 Curricula, factsheets or educational tools
3 Journal articles
1 On-farm demonstrations
1 Online trainings
2 Published press articles, newsletters
6 Webinars / talks / presentations
2 Workshop field days
2 Other educational activities: In the past, four students worked on various parts of this project for their capstone project. Currently, two undergraduate students are working on various parts of the project for their independent/capstone project. Another student is currently using a part of this project for their honors thesis. These students have been involved in soil sample collection and are able to analyze some of the preliminary data and are writing a report based on this analysis.

Participation Summary:

36 Farmers participated
4 Ag professionals participated
Education/outreach description:

On September 29th 2021, 503 high school students in Tennessee attended the Raider Roundup College and Career Exploration event where they rotated through workshops led by faculty and learned about emerging trends in agriculture and career opportunities. One rotation was focused on Soils and Soil Management in regard to land usage where the students explored the benefits of cover crops on cropping system sustainability. This event was coordinated by CoPI Dr. Chaney Mosley and the Soils and Soil Management workshop was facilitated by the PI Dr. Samuel Haruna. Further, CoPI Dr. Chaney Mosley lead soil seminar for 15 undergraduate agriculture students. After learning about soil components that promote crop growth, students selected organic materials to build desirable soil that would be used in raised vegetable garden beds located on the MTSU experiential learning lab. Additionally, research sites have been used for educational purposes by the PI (Dr. Samuel Haruna) including Soil and Water Conservation, and Soil Fertility and Fertilizer classes.

In Kentucky, CoPI Dr. Edwin Ritchey has provided advice to over 36 producers on cover crop usage and management for improved cropping systems sustainability in a changing global climate. Besides this advice, Dr. Ritchey also made the following presentations where he either demonstrated or stressed cover crops and cropping systems sustainability in a changing global climate. Please note that they are listed below using the format: title of presentation, date, and (number of participants);

  1. Wheat (cover crop) Field Day – Dealing with soil compaction – virtual, 5/11/2021, (75 participants).
  2. Kentucky Agriculture Training School (KATS) – Crop scouting training, 5/20/2020, (25 participants).
  3. Kentucky Crop Scouting Competition – 7/22/2021, (40 youths, 60 total participants).
  4. Christina County (KY) Master Gardner Soils Class – 11/21/2021, (25 participants).
  5. Henderson County (KY) Master Gardner Soils Class – 1/27/2022, (15 participants).
  6. Butler County (KY) Area Forages Fertilizer Meeting – 2/1/2022, (35 participants).
  7. Kentucky Agricultural Training School (KATS) – Questionable fertilizer products and situations, 2/22/2022, (15 participants).
  8. Marshall County (KY) Adult Grain Meeting – 2/28/2022, (15 participants).
  9. IPM Meeting – Lime and Liming Products, 3/9/2022, (80 participants).

Further, Dr. Ritchey’s work related to this project has been published in Corn and Soybean Newsletters (93 recipients) and Wheat Science Newsletter (149 recipients). These publications are available upon request.

During the second year of this project, 2 classes have been modified to include activities in this project these classes include Soil and Water Conservation (PLSO 4370) and Soil Fertility and Fertilizers (PLSO 3350), both at Middle Tennessee State University. Preliminary results have been used as teaching examples and field sites have been used for hands-on experience in these classes.

During the third years of this grant, we will conduct seminars and field demonstration for farmers, students and citizens in the collaborating states (Tennessee, Kentucky, and Alabama).

Learning Outcomes

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

Project Outcomes

1 New working collaboration
Project outcomes:

Currently, working collaboration is being developed with researchers at the University of Missouri to enhance the capacity of researchers in analyzing soil microbial activity. Another collaboration has been developed with an extension educator at the University of Tennessee on ways to improve farmer participation in scientific research. These new collaborations will be beneficial to producers in Tennessee and Missouri

Information Products

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.