Progress report for LS23-383
Project Information
Diversification of cropping systems by increasing number or type of cover crops in crop rotation plays an important role in improving land-use efficiency and in promoting sustainable agriculture. Preliminary data indicate that the implementation of cover crops in cropping systems may provide a myriad of ecosystem services in agricultural systems. Among the ecosystem services provided, one can have increasing soil organic carbon sequestration, breaking pest and disease cycles, reducing erosion and nitrate leaching, and decreasing weed pressure. Moreover, integrating livestock into cropping systems, by grazing cover crops into a crop rotation system, has the potential to promote increased market diversification, increased economic return, enhanced nutrient cycling, and sustainability. Combining different forage species in the same area simultaneously in a cropping system can enhance soil quality and improve nutrient availability to crops. The combination of different functional groups of forages as cover crops has the potential to extend the benefits to improve yields and reduce nitrogen inputs, allowing for a more efficient use of resources, and reduce environmental impacts. Although some studies have investigated the effect of cover crops on cash crop production, soil and water quality, and environmental impacts, little has been done to investigate the effect of intercropping and grazing multi-species cover crops on the whole cropping system, from cover and cash crops to animal production and other ecosystem services. The objective of this proposal is to 1) evaluate how different grazed cover crops systems consisting of an annual grass as monoculture or in combination with a legume or with legume-brassica mixture influences the plant, animal, and environmental interfaces, 2) determine the best combination of different varieties of oats and crimson clover in the Southeast, 3) assess the contribution of cover crop use on soil organic matter formation and greenhouse gas emissions, and 4) create a reference booklet to increase awareness of the benefits of legumes in the forage systems in the Southeast. The project team, consisting of two livestock specialists, two forage specialists, one plant breeder, and a postdoctoral fellow, will implement the mixtures as cover crops in an already established cotton cropping system to determine forage agronomic characteristics, animal performance, soil health parameters, and environmental impact parameters over two years. This study will provide Southeastern crop producers with science-based information and recommendations on utilizing diversified cover crops in crop rotation systems to improve their farming systems profitably and sustainably. Three field days will be held over a 3-year period to disseminate the findings to crop producers throughout the states of Alabama and Florida. Findings from the study will also be published using established social media outlets and online websites (e.g., alabamaforages.com). Extension and peer-reviewed articles will be submitted during Year 3 of the proposal. Transfer of knowledge to crop producers will be assessed to evaluate the impact of the outreach program. The proposed booklet will be distributed at the International Grassland Council meeting in May 2023 (n = 500 copies) and other forage-related.
- Determine the effect of grazing multi-species cover crops on soil characteristics and cover crop performance and to understand the role of cover crops on soil organic matter formation.
- Determine the effect of grazing multi-species cover crops on forage production and quality and animal performance.
- Determine the effect of grazing multi-species cover crops on commodity crop yield.
- Assess the level of genotype-by-management interaction of multi-species cover crops.
- Develop an Extension and outreach program to create awareness on and disseminate knowledge of multi-species grazed cover crops to farmers, Extension agents, and researchers.
Cooperators
- - Producer
- - Producer
- - Producer
Research
In order to meet objective 1, we plan to evaluate how a grass-only, grass+legume, and grass+legume+brassica cover crop effects soil nutrient cycling, cover crop yield and decomposition when either grazed or not grazed by beef cattle. In the Fall of 2023, four cover crop paddock treatments (Grass, Grass+Legume, and Grass+Legume+Brassica) will be randomly established on 20 acres of a cotton-peanut cropping system following commodity crop harvest. Plots will be established at the Wiregrass Research and Extension Center (WREC) and at two cooperating farms in South Alabama. Paddocks will be divided into two subplots randomly assigned to grazing or no grazing and replicated three times at each site. Prior to planting in Fall 2023, 20-cm soil cores will be taken for determination of soil N, C, P, K, pH, and bulk density on all four research sites. Data will be collected at the research stations and two cooperating farms. Soil quality characteristics will be evaluated pre and post grazing. For soil organic matter and nitrogen 20 soil samples will be randomly collected, dried, sieved through a 2-mm screen, and ball milled for carbon and nitrogen analysis using an elemental analyzer. Soil compaction will be measured as soil strength using a tractor-mounted hydraulic, five-probe penetrometer to obtain cone-index values for each paddock at multiple depths. The research project will be repeated in Year 2 (Fall 2024-Spring 2025) using the same sites and cover crop treatments. After the second commodity crop harvest (Fall 2025), 20 cm soil cores will be taken for determination of soil N, C, P, K, pH, and bulk density. Soil samples will be collected at 0-15 cm and 15-30 cm then placed in the dryer at 55°C for 48-72 h and then weighed. We will then thoroughly wash the roots using a sieve and dry again at 55°C for 48-72 h. Root mass biomass will be expressed per gram of soil and within each soil layer (0-15 and 15-30 cm).
At UF IFAS NFREC Marianna, we will investigate the role of cover crops on soil organic matter formation. The experiment will have different types of cover crops and management combination, as follows: 1. Oats without grazing; 2. Oats + crimson clover and grazing; 3. Oats + crimson clover + 30 lb N/acre and grazing; 4. Oats + 80 lb N/acre and grazing. Treatments are allocated in a randomized complete block design with 3 replications. Plots measure 24 x 50 ft. and they are mob-grazed every 14 days. The experiment follows a crop rotation with 2 years of cotton and 1 year of peanut. Row crops are planted during the warm-season and cover crops during the cool-season. Grazing commences when cover crop biomass is greater than 1,000 lb DM/acre, which is also the residual biomass after each grazing event. Before cover crop termination, two enrichment chambers (2 x 2 ft each) will be placed on each experimental unit (total of 24 chambers). Chambers will be translucid and have a septum to inject 13C enriched CO2 to label the biomass. Furthermore, 15N labelled urea will be applied at a rate of 0.5 lb N/acre to label the residue with 15N. The dual labelling approach will be used to track the fate of the C and N from the cover crop in the soil organic matter formation. Chambers will be placed daily, one hour after sunrise, for a 30-d period. A small fan and ice trays will be placed inside the chambers to keep it cool avoiding the shutdown of photosynthesis. The chambers will stay on for 2 h or until reaching 85˚F, whatever happens first. After the enrichment period, the biomass inside the chamber will be harvested at ground level, and the roots will be collected down to 8” depth. Above ground enriched biomass will be incubated in PVC rings for 10, 20, 40, 80, and 160 days. At the end of each incubation period, soil samples from 0-1”, 1-2”, 2-4”, and 4-6” layers will be collected and analyzed for soil organic matter fractions (POM and MAOM). At the end of this project, we expect to understand the underlying mechanisms helping to build soil organic matter and soil health in integrated crop-livestock systems.
To meet objective 2, we plan to evaluate how a grass-only, grass+legume, and grass+legume+brassica cover crop effects forage biomass production, forage nutritive value, forage in vitro digestibility, animal body weight gains, and animal enteric methane production when grazed by beef cattle. Grazed treatments will be continually stocked, and forage measurements will be conducted every 14-d for herbage mass, botanical composition, forage nutritive value (crude protein, in-vitro organic matter digestibility, fiber fractions, and micronutrients). Animal growth performance will be evaluated by weighing yearlings on electronic scale every 28 days.
To meet Objective 3, we plan to evaluate how a grass-only, grass+legume, and grass+legume+brassica cover crop effects cotton and peanut crop yield when either grazed or not grazed by beef cattle. Following the cover crop, cash crop production will be measured by mechanically harvesting a 25-m area at the center of each paddock, and subsample will be air-dried in a greenhouse, ginned, and determined for lint yield. Cash crop performance (stand counts after establishment and yield) in each paddock will be determined during the fall harvest each year. Total expenses per acre (cash crop, cover crop, and animal costs) will be recorded and used for economic analysis of treatments after conclusion of experiment.
In order to meet Objective 4, we will establish a grazed cover crop breeding pipeline by assessing the level of genotype-by-management interaction as well as the general and specific mixture performance of legume and grass breeding lines with a small plot mixture-vs-monoculture trial. In the Fall of 2022, we have established crimson clover breeding at Auburn leveraging existing Auburn and NPGS-sourced germplasm. We are also evaluating small-plot techniques for clover and oat mixture breeding. For this SSARE project, we anticipate selecting the best 30-50 candidates from this year, to be evaluated in mixture trials starting in Fall 2023. PI Wolfe will collaborate with Steve Harrison at LSU (developer of RAM forage oats) and Ali Babar at UF, to source 30 suitable oat candidates for 2023 and 2024 trials. Depending on seed yield and results from our preliminary mixture trials underway this year, we will establish mixture plots as either single-rows (5-10’ long) or as 30” wide (4 x 7.5” spaced rows) by 5-10’ long.
Seed from each candidate will be evaluated in 3 treatments: monoculture, crimson-oat mixture and crimson-oat-turnip mixtures. Within each treatment, rather than testing all pairwise combinations, which with 45 clovers and 30 oats would amount to 1350 plots/rep, we will use a partial factorial experimental design. In each rep, all families of crimson will be tested against several genotypes of oats, the same will be done for each oat genotype, ensuring each genotype of each species is evaluated with several companions. Our goal will be to replicate each oat and clover in monoculture, in mixture with at least three companions, and again in mixtures also containing the T. raptor Turnip. As little as 525 small plots/year will be required in this design. Biomass, botanical composition, weed suppression and forage quality by NIR will be scored on mixture and monoculture plots. We will repeat the trial in the 2024-2025 season. Mixed-model analyses of the entire trial will be used to estimate GxM variance. GMA and SMA will be assessed for each trait in each species using the mixture data.
We will use a genotyping-enabled breeding approach to allow assessment of performance even for clover-oat combinations that we did not test in our partial factorial experiment. We will genotype all clover and oat entries with a low-cost DNA marker platform, most likely genotyping-by-sequencing (Elshire et al. 2011). This will enable us to do something that has been proposed in the literature (Wolfe et al. 2021; Bourke et al. 2021), but not yet tested, using genomic prediction to “fill-in-the-blanks”, predicting the performance of the clover-oat combinations. This kind of approach is used in e.g. hybrid maize breeding (Zhao, Mette, and Reif 2014; Wang et al. 2020), to enable better selections of hybrids, earlier in a breeding pipeline, leading to better results downstream.
In the Fall of 2022, we have established crimson clover breeding at Auburn leveraging existing Auburn and NPGS-sourced germplasm. We are also evaluating small-plot techniques for clover and oat mixture breeding. For this SSARE project, we anticipate selecting the best 30-50 candidates from this year, to be evaluated in mixture trials starting in Fall 2023. PI Wolfe will collaborate with Steve Harrison at LSU (developer of RAM forage oats) and Ali Babar at UF, to source 30 suitable oat candidates for 2023 and 2024 trials. Depending on seed yield and results from our preliminary mixture trials underway this year, we will establish mixture plots as either single-rows (5-10’ long) or as 30” wide (4 x 7.5” spaced rows) by 5-10’ long.
To meet Objective 5, we will create a legume+forb reference guide to assist farmers and Extension agents in best management practices for establishing and managing legume and forb forage systems. At least four field days will be used to demonstrate and encourage adoption of grazed cover crops in a sustainable livestock and row crop production system. Lastly, research results will be disseminated through Extension and research-type articles to provide farmers, Extension agents, and researchers with information to assist with development of farm-specific grazed cover crop management strategies. We will develop an Extension and outreach program to disseminate knowledge of multi-species grazed cover crops to farmers, Extension agents, and researchers. Specifically, we will create a legume+forb reference guide to assist farmers and Extension agents in best management practices for establishing and managing legume and forb forage systems. At least four field days will be used to demonstrate and encourage adoption of grazed cover crops in a sustainable livestock and row crop production system. Lastly, research results will be disseminated through Extension and research-type articles to provide farmers, Extension agents, and researchers with information to assist with development of farm-specific grazed cover crop management strategies.
On the third cooperating farm, located in North Alabama, cover crops will be established in the Fall of 2023 and Fall 2024 and grazed under a mob-grazing system with cow-calf pairs. This farm will utilize a 10-species blend of grasses, legumes, and forbs on 25 acres. This farm is not currently producing row crops but will provide a demonstration site for row crop and beef cattle producers alike for agronomic and grazing management, use of multi-species cover crop/forage blends, and forage/cover crop productivity. On this site, initial soil samples will be taken for determination of soil N, C, P, K, pH, and bulk density. Every 14-d forage/cover crop samples will be taken for determination of biomass and nutritive value. The producer will also keep records of animal number and body weight per acre and grazing time during daily grazing allotments.
Laboratory Analyses
Soil
Due to the large size of grazing paddocks (~1.75 acre), soil variability is expected to be high within each paddock. To target our soil sampling scheme more efficiently, soil will be mapped using Veris® to characterize soil conductivity at project initiation. Soil samples will be collected annually from depth intervals of 0-5, 5-10, 10-15, and 15-30 cm two weeks after cover crop termination. At minimum, fifteen sub-samples from each depth will be combined to form a composite sample for laboratory analysis. Each year, soil samples according to depth will be analyzed for inorganic N, Mehlich1-extractable nutrients, phosphorus fractionation, active carbon, aggregate stability, and soil microbial biomass. Total soil organic carbon will be measured during the first year of the project and following four years of cover crop incorporation for soils collected after cover crop termination.
During the cash crop season, soil penetration resistance, soil water infiltration, and mycorrhizae colonization will be measured. Soil penetration resistance will be measured in situ each year approximately one month after planting cash crops. Saturated conductivity of soils will be measured with a single-ring infiltrometer. Mycorrhizae counts will be measured for cotton and peanut when respective crops are in rotation.
Forage/Cover Crop
Forage samples will be taken every 2 weeks during the grazing season and be a composite of 6 random 0.25 m2 subsamples in each paddock. A final forage biomass sample will be taken from all paddocks just prior to cover crop termination. Sub-samples from the final forage biomass sample will be placed into decomposition bags. Decomposition bags will be collected at 4, 8, and 12 weeks after cover crop termination to assess cover crop decomposition rates, an indicator of residue ground cover. Forage samples will be analyzed for total N, total P, total C (LECO), neutral detergent fiber, acid detergent fiber, lignin (ANKOM), and micronutrients (ICP). A pre-harvest cash crop biomass sample will also be collected from each paddock and analyzed for total P and N.
To determine in vitro digestibility and enteric methane production, forage samples will be hand plucked every 14 days from the non-grazed treatments, dried for 48 h at 60°C, and ground through a 2-mm screen. Samples will be fermented for either 2, 4, 8, 24, 48, or 72 hours. Batch culture digestion will be conducted at the Auburn University Ruminant Nutrition lab. In-vitro dry matter digestibility in all samples at all timepoints. Volatile fatty acids and methane will be analyzed in the 72-h samples only by gas-liquid and gas chromatography, respectively.
Preparations for Year 1 (Winter 2023-2024) are being made. Meeting with cooperating farmers is being scheduled for July.
The research conducted in Year 1 at both sites was successful. Both sites are currently grazing cover crops. Our cooperators are also grazing and will begin planning on-farm field days for Fall 2024 and Spring 2025.
Education
To date, a producer field day has been conducted at the Wiregrass Research and Extension Center in Headland, AL. This field day was attended by 64 producers. An additional field day was conducted at a cooperating farmer (Tim Tucker, Monroeville, AL) in Jan 2024. It was attended by 98 producers, government employees, graduate students, and research and Extension faculty from across the U.S. Data from Year 1 of research was also presented at the Southern American Society of Animal Science meeting in Louisville, KY. The audience was graduate students, research and teaching faculty, and Extension specialist from around the Southeast.
Educational & Outreach Activities
Participation Summary:
The outreach plan for this project will include workshops, printed materials, producer and scientific conferences, and online resources for Alabama row crop and livestock producers and members of the scientific community. These materials will address the economic and environmental sustainability of grazing multi-species cover crops in the Southeast. During the outreach phase of this proposal, several challenges will need to be addressed. The main challenge to adoption of integrated crop livestock systems in the Southeast. As a result of crop intensification, many row crop fields do not have permanent fencing, nor do row crop producers own or manage cattle themselves. As a result of this project, the investigators are hoping to increase awareness and willingness among Alabama and Florida producers to introduce grazed cover crops on to their farm. Information gleaned from the research portion of this study will be important to indicate to producers the positive and negatives of cattle introduction into row crop fields.
In the Fall of 2023, we will produce an ACES publication entitled ‘Use of Legumes and Forbs in the South.’ This will be a peer-reviewed, producer-orientated publication that will address the economic and environmental components of annual and perennial legumes and forbs (e.g., brassicas) in grazing systems. It will also discuss establish and management strategies to ensure a season-long, productive forage system. It will discuss the soil testing, legume, grass, and forb monocultures and mixtures, proper establishment, grazing management, and integrated pest management considerations. A section on weed management and proper herbicide applications, as well as scouting and treatment of common pests (e.g., d fall armyworms) will also be included. This publication will be available to producers at workshops in printed formats, will be featured in the Alabama Forages eNewsletter (250 participants) and on the Alabama Forages Facebook page (2100 participants), as well as through the UF-IFAS website and social media. It will be sent to regional and county-level extension agents in Florida and Alabama, as well as Extension professionals in surrounding Southeastern states. This will allow for further dissemination to Southeastern row crop and livestock producers. A second peer-reviewed Extension publication will be released in the Fall 2024 featuring specific cover crop blends for maximizing cattle production and ecosystem services of cool-season annual mixtures. This publication will cover major cool-season annual forage species, planting dates and rates, and livestock management considerations for grazing cover crops to minimize effects on the production of the cash crop. This publication will be released to producers in the same method as the first publication.
Three workshops will be held in Alabama and one workshop in Florida at participating producer farms and research stations. All cooperating producers have agreed to host and/or participate in these workshops. The curriculum will be similar at all three field days, with changes based on crop and management differences. Each field day will consist of formal instruction (e.g., PowerPoint presentations) and field demonstrations. The topics that will be covered will include: 1) Cover Crop Species Selection 2) Soil Testing and Fertility; 3) Grazing Demonstration 4) Temporary Electric Fencing; 5) Calculating plant residual biomass to ensure proper cover; and 6) Grazing and cutting height and their effects on soil root growth demonstration. These workshops will tentatively be scheduled for Spring 2024 and 2025.
The results of this experiment will be featured 2 times (once per yr in 2024 and 2025) on the Alabama Forage and Animal Science eNewsletter: Research Update. This eNewsletter was created in March 2018 and currently has 1500 followers. The investigators expect the number of participating producers to increase to 350 or more before the release of these articles. Two state-based popular press articles (e.g., Alabama Cattleman’s Magazine and Florida Cattleman’s Magazine) will be written (one per year in 2023 and 2024) related to cool-season annual forage mixtures and integrated crop-livestock systems. These publications currently has a readership of over 12,000 cattle and forage producers per state. Furthermore, one article discussing integrated crop-livestock systems will be written and submitted to Progressive Forage Grower or Hay and Forage Grower magazines and a second article on the grazing strategies for cool-season annual forages. These magazines have an international readership and have over 45,000 subscribers, respectively.
In addition to outreach to producers, information will be disseminated to other forage Extension and research professionals at regional and national scientific conferences. After completion of Year 1, scientific abstracts will be submitted to 2 regional scientific meetings. In July 2024, the graduate student assigned to this project will present the findings from Year 1 at the National Meeting of the American Society of Animal Scientists. An additional abstract will be presented to the Southern and Forage Pasture Crop Improvement Conference in July 2024. After completion of Year 2, final experimental results will be presented at the Southern Pasture and Forage Crop Improvement meeting in July 2025 and the Annual American Society of Agronomy meetings in November 2025. In addition to scientific abstracts, the results will be summarized in a three peer-reviewed manuscripts that will be submitted to the Crop, Forage, and Turfgrass Management Journal in Fall 2025. The topic of these articles will be the On-farm Research and Extension programs, data from the North Florida Research station and the Wiregrass Research Station, and the last manuscript will focus on data from the small plot research trial to determine genotype and management differences in multi-species cover cropping systems.
Outreach programming will start in Spring 2024.
Learning Outcomes
Cover Crop Species and Variety Selection
Grazing Management
Project Outcomes
The team is currently working with a larger group from the University of Florida, University of Georgia, USDA-Agricultural Research Service, and Auburn University on a USDA-SAS grant that will be submitted in July 2023. If funded, this grant will expand the current project by the addition of other cover crop management systems, as well as farmer surveys to determine cause of low cover crop adoption in the Deep South.
This grant was not funded, but it being resubmitted in Summer 2o24.