Selecting cover crops for diverse functions: an integrated soil management approach for organic strawberry production in North Carolina

Selecting cover crops for diverse functions: an integrated soil management approach for organic strawberry production in North Carolina

Summary

We have initiated a field experiment comparing seven summer cover crops and combinations (Sudan grass, Velvetbean, Sudangrass/Velvetbean, Pearl millet, Soybean, Pearl millet/Soybean, and Rape) to a control (no cover crop) treatment for their effects in organic strawberry production. All cover crops performed lower than expected because of 2007 drought. Sudangrass produced the highest biomass and all were adequate at weed control except Rape. We initiated three on-farm trials to examine benefits and management of selective cover crops with strawberries. Strawberry yield, nutrient and mycorrhiza responses are being analyzed from the field experiment and will be collected in on-farm trials spring 2009.

Objectives/Performance Targets

• The overall objective of this study is to develop an integrated approach of cover crop rotations and beneficial AM fungi management as sustainable soil and pest management practices for organic strawberry production in North Carolina. Our specific objectives for this project are to:

  Evaluate seven cover crop species and combinations (Sudan grass, Velvetbean, Sudan grass/Velvetbean combination, Soybean, Pearl Millet, Soybean/Pearl Millet combination, and Dwarf essex rape) compared to a control (no cover crop) for their impact on strawberry yield and ability to enhance indigenous arbuscular mycorrhizal (AM) fungi in organic strawberry production systems. This large research field study will occur over two strawberry seasons at the Center for Environmental Farming Systems in Goldsboro, NC.

  Evaluate strawberry yield benefit from indigenous AM fungi and commercial AM fungi inoculum sources.

  Develop on-farm trials with three strawberry producers in North Carolina for evaluation of selected cover crop species and their effect on indigenous AM fungal diversity and strawberry yields.

  Promote technology and education transfer on cover crop and AM fungi management in organic and conventional strawberry production systems among farmers, extension agents, NRCS agents, the NC Strawberry Association, researchers and students.

Accomplishments/Milestones

• The field study at the Center for Environmental Farming Systems (CEFS) in Goldsboro, NC was initiated in June 2007. This research study will examine seven different summer cover crop treatments consisting of sudan grass, velvet bean, sudan grass/velvet bean combination, pearl millet, soybean, pearl millet/soybean combination, dwarf essex rape and a non-cover crop treatment (control) for their subsequent effects on strawberry yields and the beneficial arbuscular mycorrhizal fungi community over two years. Baseline soil fertility, nematodes and mycorrhizal fungal communities were sampled in May before cover crop treatments were established mid June 2007 (planting time would be similar for strawberry producers in North Carolina). Cover crops were assessed for their biomass responses, shoot nutrient response and effects on weed abundance and diversity and subsequently cut and tilled in late August 2007 to prepare for strawberry beds. Strawberry tips (Chandler variety) were inoculated with either indigenous mycorrhizal fungi or selected commercial mycorrhizal fungal inoculant (previously examined to have the highest root colonization among a trial of three commercial mycorrhizal inoculants) for four weeks prior to planting in October 2007. Strawberry growth, nutrient responses and yield were assessed from Dec 2008 through early June 2008. The field study was tilled post harvest and summer cover treatments were re-established in mid June 2008 through early September 2008. New strawberry tips inoculated with the same native or selected commercial mycorrhizal fungal inoculant as the previous year were planted early October 2008. Similar strawberry growth, nutrient and yield responses will be examined December 2008 through the second harvest period (end of April through early June 2009).

  Three on-farm research trials have been established with producers in Calabash, Burlington, and Apex, NC. The three farms represent different soil and climatic conditions for strawberry production and all the three producers have a strong interest in using and knowing more about management of summer cover crops for strawberries. The project coordinator and graduate student met with all three strawberry producers to discuss project details, responsibilities select specific cover crops for specific farm conditions early 2008. On every farm, we have established two cover treatments and a control (no cover crop) treatment with each treatment replicated three times for a total of nine plots. Specific cover crop species may differ for each farm depending on the specific farm conditions and management considerations. Plots were established and cover crops planted mid June 2008 on all three farms. Prior to planting, baseline soil nutrients, nematodes and mycorrhizal fungi diversity were sampled at each farm. Cover crops were examined for their biomass, nutrient and weed control response prior to cutting and incorporation in preparation for strawberry planting in October 2008. Although all of the three farms in this study are managed with conventional methods typically using methyl bromide, one of the farms opted not to use methyl bromide in the on-farm research plot and we will assessing any yield or pathogen differences in this plot. Strawberries were planted on all the farms in October 2008 and we will be assessing strawberry yields with the help of the producers this spring 2009.

  Project leaders Michelle Schroeder-Moreno and Gina Fernandez and graduate student Ben Garland spoke to strawberry growers, the director of the NC Strawberry Association, and local Natural Resources and Conversation Services agents at a Strawberry Conservation Field Day on March 25 2009. This field day was organized by the NC Strawberry Association and occurred on the Apex farm (Buckwheat farms) one our on-farm trial of cover crops were. We discussed the project, answered questions about cover crop management and cover crops were discussed in context with other alternatives to methyl bromide. Evaluation of cover crop species for diverse functions, including enhancing AM fungi is a major advancement towards developing an integrated approach for sustainable soil and pest management in organic and conventional strawberry production in North Carolina and the Southeastern United States.

Impacts and Contributions/Outcomes

• Evaluate various summer cover crops and their combinations for their effects on strawberry yields and nutrient uptake, weed management, soil nutrient properties, effects on the beneficial mycorrhizal fungi, and overall suitability in strawberry production systems for North Carolina. Results from this research on cover crops can be extended to producers throughout the Southeast US that are managing strawberries either organically or conventionally.

  Compare strawberry yield benefit from indigenous mycorhizal fungi compared to a selected commercial AM fungi inoculant in field conditions in an organic production system.

  Examine how cover crop species affect mycorrhizal fungi community and subsequent strawberry growth and nutrient responses.

  Identify farm-level benefits and potential management or other challenges to using summer cover crops in various strawberry production systems.

  Educate researchers, extension agents, producers and students about summer cover crop benefits and management and beneficial mycorrhizal fungal management for conventional and organic strawberry production systems in North Carolina and the Southeast.

Collaborators: