Evaluating On-Farm Use of Multi-Species Cover Crops

View the project final report

Commodities

• Agronomic: corn, cotton, soybeans

Practices

• Crop Production: cover crops
• Education and Training: demonstration, farmer to farmer, on-farm/ranch research, technical assistance, workshop
• Natural Resources/Environment: soil stabilization
• Soil Management: soil analysis, soil chemistry, soil microbiology, soil quality/health
• Sustainable Communities: partnerships

STATEMENT OF PROBLEM

By 2050 the world is projected to gain an additional 2 billion people. Experts predict that food production will need to increase by 50% to 70% to feed and clothe the increased population. The project partners recognize that the Southeastern USA has a preponderance of low quality soils. National soil degradation is directly linked to conventional agricultural practices of excessive tillage and leaving fields bare between plantings of cash crops. Soil health improvements are vital to enhancing the ability to grow more food for the rapidly increasing world population while minimizing impacts to natural resources. North Carolina's number one economic driver is agribusiness with an annual impact of $84 billion dollars. North Carolina is also experiencing a rapidly expanding population impacting land use while the face of agriculture is changing. From moratoriums on animal production agriculture to an expansion in organic farming and the tobacco buyout program, now is the time to evaluate and introduce improved agriculture management techniques that will positively impact soil health.

Project partners want to learn how multi-species cover crops can benefit soil health while positively impacting on-farm sustainability in Southeastern farming systems. Soil health is defined as the continued capacity of soil to function as a living ecosystem. According to Managing Cover Crops Profitably, 3rd Edition, SARE, June 2012, cover crops improve soil structure, increase infiltration and water holding capacity, increase cation exchange capacity (allowing for more nutrient storage), and improve long term nutrient storage (nutrient banking). In the national 2012-2013 Cover Crop Survey conducted by the Conservation Technology Information and North Central SARE, the top challenges of adopting cover crops relate to establishment, cost, species selection, and management. The use of monoculture cover crop in conservation tillage production systems has been widely adopted in the Southeast; but the use of multi-species cover crops is far less prevalent. Consequently, information on establishment guidelines and soil health benefits has been borrowed from Midwest farming systems. Cropping systems, soil types, and climatic environments in the Southeast are notably different from those in the Midwest, such that scientifically documented and practical knowledge is not readily transferable. NRCS held a national forum on the Soil Health Initiative in February 2014. Satellite discussions were held at various locations in North Carolina. At the Nash County event, over 50 attendees participated with producers representing 6 counties. Districts reported that the forum created excitement on the concept of soil health. Producers wanted to see demonstrations of multi-species cover crops before considering whole farm adoption. Project partners started this endeavor with some simple questions. What are the short-term soil health benefits of multi-species cover crops? How do we change traditional farming practices in the Southeast to start to incorporate the benefits of multi-species cover crops?

STATEMENT OF PROPOSED SOLUTION

North Carolina is well positioned to act as a pilot evaluation area for multi-species cover crop best management practices and elucidate short-term fluxes in soil chemical, physical, and biological properties due to a favorable winter climate. North Carolina has a variety of cropping systems, soil types, and climate variations across the physiographic regions stretching from the mountains, to the Piedmont, and the coastal plane. Moreover, the knowledge gained from these broad geographic areas would be transferable to similar landscapes throughout the Southeastern USA. North Carolina is uniquely situated to facilitate the project since agribusiness is the number one economic driver, three physiographic regions allow for testing in a variety of cropping and climate situations, and the strong conservation partnership has a proven track records of delivering positive results that can be replicated in neighboring states. New management techniques are more readily adopted regionally when a local farmer is successful at the county level and farmer-to-farmer training occurs with multi-species cover crops being the next pilot project fitting the mold. The longer-term benefits of multi-species cover crops include reductions in input costs and providing effective mitigation against droughts and pest infestations. Demonstration projects are needed to reinforce proper management of multi-species cover crops such as proper time of planting, allowing for a greater accumulation of biomass and nitrogen, and proper time of growth termination that can be done effectively without using tillage. Soil functions are improved by the following principles: minimize soil disturbance, increase plant diversity to positively impact microbial and nutrient diversity, keep a living root growing year round, and keep residual cover at the surface as long as possible.

The primate goal of this project is to demonstrate to producers that a diverse mixture of cover crops, properly managed, will increase soil functions and can lead to a more sustainable farming system.

APPROACH AND METHODS

Project partners received $15,000 in funds to build upon the NC Foundation for Soil and Water Conservation's soil health initiative to determine the early signs of soil health benefits of multi-species cover crops and promote adoption of the conservation practice. Other project funding sources include Cotton Incorporated, the NC Agriculture Development and Farmland Preservation Trust Fund and the USDA Natural Resources Conservation Service's Conservation Innovation Grant program. Southern SARE On-Farm Research Grant Program's funds will be used to offset additional sampling analysis, establish additional in-field data collection systems and overall program management.

The Foundation secured demonstration plots with local producers, in conjunction with soil and water conservation districts (Districts) in Alamance, Ashe, Davidson, Edgecombe, Henderson, Madison, Nash, Rowan, Stanly, and Wake counties. The Foundation is collaborating with NC State University's Department of Soil Science with Dr. Wagger then Dr. Broome, and the Department of Crop Science with Dr. Reberg-Horton and Sarah Seehaver. The Foundation is also partnering with Dr. Franzluebbers with USDA Agriculture Research Service. Technical guidance is provided by Mr. Woodruff and Mr. Lowder with the USDA Natural Resources Conservation Service's East National Technology Support Center. Each District has formed a local workgroup composed of farmer cover crop advocates, North Carolina Cooperative Extension agents, Natural Resources Conservation Service, NC Department of Agriculture and Consumer Services' regional agronomists, and other interested parties.

The Districts partnered with a local producer that is using conservation tillage practices and has an interest in the next level of soil health management. Each demonstration is 5 to 10 acres in size and was established in 2014 (3 sites) to 2018 (10 sites). The demonstrations are established with alternating rows of monoculture cover crop or no cover crop to allow for statistical comparisons per field. Project partners will use the farms themselves as multiple observations of common treatments across farms. Districts are hosting annual soil health field days with a focus on farmer-to-farmer interactions and sharing lessons learned.

To refine best management practices for multi-species cover crops in North Carolina, the following factors are being evaluated: 1) Seed mixtures with a minimum of 4 cover crop species, 2 of which are legumes, taking into consideration crop nitrogen requirements and impact on cash crop yield potential. 2) Cover crop seeding method (drilling, overseeding prior to cash-crop harvest, or self-reseeding, and broadcasting with or without incorporation). 3) Cover crop seeding dates (e.g. early September, late September, October, and November). 4) Cover crop termination strategy (chemical desiccation, roller crimper, or both).

To determine the short-term benefits of multi-species cover crops in no-till and reduced till production systems, project partners will document changes in soil properties, as well as yield improvements. Project partners are documenting nutrient cycling benefits by evaluating results of soil tests for realistic yield expectations and various forms of soil organic matter, including soil microbial activity with the Solvita Soil CO2 Burst test (http://solvita.com/soil). Nutrient availability to plants will be documented with nutrient uptake of cover and cash crops. Some notable short-term changes in soil properties and nutrient cycling are noted in the preliminary results of the 2015-2016 cover crop demonstrations.

Surface-soil samples are collected from crop production fields in winter/spring by compositing 8 cores (4-cm diam) to represent depths of 0-6, 6-12, and 12-20 cm following collection of surface residue mass from 0.04 m2 areas at each of the coring locations (Franzluebbers et al., 2001). Soil will be split into two fractions following initial screening and mixing through 8 mm openings: (1) dried at 50°C, sieved to pass a 4.75-mm screen to determine chemical and physical properties and (2) kept moist at 4°C, sieved to pass a 2-mm screen to determine soil microbial communities.

The following properties will be determined from this sampling scheme:
1) Soil C and N fractions; (i) total with a Leco Tru-Spec CN analyzer, (ii) particulate organic matter with dispersion and sieving (Cambardella and Elliott, 1992; Franzluebbers et al., 1999b), (iii) microbial biomass with chloroform fumigationincubation (Jenkinson and Powlson, 1976; Franzluebbers et. Al, 1999a), (iv) inorganic N from 1:2, soil:2 M KCl extraction and colorimetric determination of NH4 and NO3 with automated, segmented-flow analyzer.
2) Surface residue C and N: Leco Tru-Spec CN analysis of ground (<1mm) residue along with dry weight determination of total mass.
3) soil bulk density: dry-weigh and volume of cores.
4) Soil microbial community structure: substrate utilization for bacterial and fungi on BIOLOG plates (Buyer el al., 1999; Buyer et al., 2001).

Additionally soil moisture availability will be documented by deploying moisture sensors and support technology, specifically Acclima water sensors and particle electron processors with 3G Cellular data transmitters. Data will be collected to document increased infiltration and retention of water. Leaf roll scoring will be tracked to determine the time of day the cash crop denotes signs of heat stress. The data will be correlated to soil moisture and allow for recommendations regarding effective water conservation methods and practices to increase infiltration.

Plant samples are collected from the cover crop for determination of biomass, botanical composition, and nutrient content. Three areas (0.5 x 0.5 m square) will be cut in each cover-crop treatment observation and sorted for discernible plant components and each component weighed separately after drying for at 50°C for 3 days. Dried samples are analyzed for C and N concentrations using dry combustion. Crop yield is determined either from strip-level determinations from the producer or from 3 randomly collected 1 m2 areas for easy treatment observation by project partners.

The general linear model procedure of SAS will be used to analyze variances for each of the soil (by depth), plant, and animal responses separately during each year. Soil depth, year of sampling, and within season plant biomass will be considered repeated measures and errors associate with them separated accordingly.

PROJECT RELEVANCE TO SUSTAINABLE AGRICULTURE

The overall goal of the program is to demonstrate to producers in North Carolina and throughout the Southeast that multi-species cover crops, when properly managed, will increase soil ecosystem functions and lead to improved on-farm sustainability. The project will quantify short-term changes in soil chemical, physical, and biological properties by measuring increased soil aggregation and organic matter, microbial activity, and water infiltration rates. The project will relate the short-term changes in soil properties to broader concerns for nutrient cycling within and from agro-ecosystems, overcoming soil water limitations, and improved crop yield and growth. Project partners will make recommendations to refine best management practices for multi-species cover crops in production systems common to North Carolina and neighboring states in the region. All of these lessons learned will be used to promote the increased soil health improvements from the use of multi-species cover crops regionally to increase agriculture sustainability.

Part of the program is to encourage Districts to work with producers to determine what seed mixes work best on their farms based on their specific soil types and proposed crop rotations. Each farmer is interested in testing out specific benefits such as alleviating compaction, nematode population reductions, building organic matter, and increasing N in the system. Due to the unique nature of issues being explored per farm, project partners are not recommending a specific set of seed mixes beyond the requirement to include a minimum of 4 species, 2 of which are legumes. The producers and the Districts work together to source the seed mix they want to test. Project partners are not privy to which seed mixes may contain genetically engineering varieties. The Districts indicated is it very uncommon for cover crop seed mixes to contain genetically engineered varieties. Please note Southern Region SARE funds will not be used to purchase seed for any of the demonstrations. By including Southern Region SARE funding, project partners will commit to collect data regarding the use of genetically engineering seed varieties and report back to the funder any concerns raised by their inclusion.