Enhancing Strawberry Production in the Southeastern U.S. through Summer Cover Crops, Beneficial Mycorrhizal Fungi, and On-Farm Participatory Research

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Title: Enhancing Strawberry Production in the Southeastern U.S. through Summer Cover Crops, Beneficial Mycorrhizal Fungi, and On-Farm Participatory Research
Author: Garland, Benjamin Clayton
Advisors: Michelle Schroeder-Moreno, Committee Chair
Gina Fernandez, Committee Co-Chair
Nancy Creamer, Committee Member
Abstract: North Carolina is the 4th largest producer of strawberries, with most of its production coming from small family farms that run roadside stands and pick- your-own operations. As methyl bromide fumigation will become more restrictive to use and eventually phased out in the coming years, many growers are looking for alternative strategies to maintain productivity and reduce environmental impacts. A two-year field experiment was conducted to examine the effects of eight cover crop treatments combined with two arbuscular mycorrhizal (AM) fungal inoculants on strawberry growth and yields. Cover crop treatments included two grasses, two legumes, two grass/legume combinations, a non- mycorrhizal host, and no cover crop. Mycorrhizal treatments included a mixture of native AM fungal species found at the research site, and a single species derived from a commercially available inoculant. Cover crop treatments were assessed for their aboveground biomass and nutrient uptake, as well as their impact on weed abundance and diversity, soil nutrients, parasitic nematode populations, and subsequent strawberry growth, yields, and nutrient uptake. Mycorrhizal treatments were also assessed for their impact on strawberry growth, yields and nutrient uptake. Strawberry plants were sampled five times throughout the growing season for dry weights of roots, crowns, leaves, flowers and fruit, leaf area, percent AM colonization of roots, total yield, cull yield, and marketable yield. Grass-based cover crop treatments, particularly pearl millet, produced much greater aboveground biomass compared to the other cover crop treatments. In both years, cover crops significantly reduced summer weed biomass compared to the no cover crop control. Cover crop treatments had no effect on the subsequent strawberry plant growth or yields in either year. Mycorrhizal inoculation treatments did not differ in their effects on overall strawberry yields nor plant growth, although scattered effects on plant growth were observed on some sample dates. A second one-year study was conducted on three participating farms to determine the effects of summer cover crop treatments on strawberry yields, weed biomass, and cover crop biomass, and to investigate the producer-perceived benefits and barriers to the adoption of cover crops in a real-world strawberry production system. Mycorrhizal fungi populations at each farm were also assessed. Investigators maintained an ongoing discussion with producers that culminated in a formal post-season interview that gauged their concerns surrounding the adoption of cover crops, surveyed their interest in adopting organic practices, discussed their strategies for phasing out methyl bromide, and gathered their suggestions for future research. Results showed that cover crop treatments significantly reduced weed biomass at two of the farms, but not the third. There was no significant difference between the amounts of aboveground biomass produced by the two cover crops trialed on each farm. Cover crop treatments reduced total strawberry yield compared to the bare ground control at one farm, but no difference was found at the other farm (the third farm did not participate in yield measurements). Producer interviews suggested that the most prominent barriers to adoption of cover crops are: 1) a lack of information about how to integrate cover crops into a strawberry production schedule; 2) an absence of practical guidance on how to increase cover crop biomass responses through enhanced seeding rates and other integrated organic amendment applications, 3) a need to evaluate cover crop benefits in strawberries over a longer time period, not just one season; 4) an insufficient understanding of the interactions of mycorrhizal fungi and other beneficial soil inoculants when combined together with cover crops; and 5) on-farm research should be more participatory and emphasize the producer's needs.
Date: 2010-02-25
Degree: MS
Discipline: Crop Science
URI: http://www.lib.ncsu.edu/resolver/1840.16/2884

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