Two separate studies were conducted to examine the effects of using summer cover crops as part of an integrated sustainable soil management approach for strawberry production in North Carolina that included a two-year field experiment and a one year on-farm trial. The field experiment was conducted at the Center for Environmental Farming Systems (CEFS) in Goldsboro, NC to examine the effects of eight cover crop treatments combined with two arbuscular mycorrhizal (AM) fungal inoculants on strawberry yields. Cover crop treatments included two grasses (Sudan grass and Pearl millet), two legumes (Soybean and Velvetbean), two grass/legume combinations (Sudangrass/Velvetbean and Pearl millet/Soybean), a non-AM host (Rape in year 1 and Buckwheat in year 2) and a control (no cover crop). Strawberry plugs were pre-inoculated with either a mixture of native AM fungal species or a single species derived from a commercially available inoculant. Sudan grass, Pearl millet and the Pearl millet/Soybean combination produced the highest aboveground biomass and the lowest weed biomass compared to the other treatments, although there were no significant differences among cover crop treatments for strawberry yields. Mycorrhizal treatments did not differ greatly, emphasizing the importance of the native AM fungal species.
A one-year on-farm study was additionally conducted on three separate farms to determine the effects of 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 strawberry production. While cover crops reduced weed biomass at two of the farms, cover crops did not affect yields at one farm but reduced yields at another. Interviews with producers revealed they perceived the greatest barriers to adoption of cover crops in strawberry production are: 1) lack of information about how to integrate cover crops into a strawberry production schedule; 2) absence of practical guidance on how to increase cover crop biomass, 3) a need to evaluate cover crop benefits in strawberries over a longer time period, not just one season; and 4) an insufficient understanding of any potential interactions of cover crops with beneficial organisms or pests.
The overall objective of this study is to develop an integrated approach of cover crop rotations, compost applications, and beneficial mycorrhizal fungi management as sustainable soil and pest management practices for organic strawberry production in North Carolina. Importantly, these practices can also be used by conventional strawberry growers as they transition away from methyl bromide. Our specific objectives for this project are below.
- Evaluate eight cover crop treatments that include 1) Sudan grass 2) Pearl millet, 3) Soybean 4) Velvetbean, 5) Pearl millet/Soybean combination, 6)Sudangrass/Velvetbean combination, 7) a non-AM cover crop host (Rape in year 1 and Buckwheat in year 2) and 8) control (no cover crop) for their impact on strawberry yields, growth, weeds, soil nutrients and impact on background native arbuscular mycorrhizal (AM) fungi.
Evaluate strawberry yield benefit from native 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 on strawberry yields. Producers will also be interviewed for their perceived challenges and benefits of using cover crops.
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.