The effects of eight summer cover crop treatments combined with two arbuscular mycorrhizal (AM) fungal inoculants on strawberry growth and yields were examined in a 2-year field experiment. Cover crop treatments included 1) sudangrass [Sorghum bicolor (L.) Moench cv. Piper]; 2) pearl millet [Pennisetum glaucum (L.) R.Br. cv. 102 M Hybrid]; 3) soybean [Glycine max (L.) Merrill cv. Laredo]; 4) velvetbean [Mucuna deeringiana (Bort) Merr. cv. Georgia Bush]; 5) sudangrass/velvetbean combination; 6) pearl millet/soybean combination; 7) a non-mycorrhizal host consisting of rape (Brassica napus L. var. napus cv. Dwarf Essex) and buckwheat (Fagopyrum esculentum Moench) in Year 1 and Year 2, respectively; and 8) no cover crop control. Strawberry tips were inoculated with either a native mixture of several AM fungal species or a single species sold commercially, Glomus intraradices. Cover crop treatments were assessed for their aboveground biomass and nutrient uptake as well as their impacts on weed abundance and diversity, soil nutrients, and parasitic nematode populations. Cover crop and AM treatments were assessed for their impact on strawberry growth, yields, AM root colonization, and nutrient uptake. Grass-based cover crop treatments, particularly pearl millet, produced the most aboveground biomass. In both years, all cover crop treatments reduced summer weed biomass compared with the control. Neither cover crop nor AM treatments had an effect on overall strawberry plant growth or yields in either year, although some differences existed at specific growth periods. The results suggest that cover crops are a viable strategy for reducing summertime weeds and that background, native populations of AM fungi in the soil may be just as effective as a commercially available species. It is likely that no overall yield benefit was found among treatments for two reasons: 1) nutrients, especially nitrogen, were not limiting; and 2) the cover crop growth window may have been too short for a significant impact on strawberries over two seasons.
Benjamin C. Garland, Michelle S. Schroeder-Moreno, Gina E. Fernandez and Nancy G. Creamer
John E. Beck, Michelle S. Schroeder-Moreno, Gina E. Fernandez, Julie M. Grossman and Nancy G. Creamer
Summer cover crop rotations, compost, and vermicompost additions can be important strategies for transition to organic production that can provide various benefits to crop yields, nitrogen (N) availability, and overall soil health, yet are underused in strawberry (Fragaria ×ananassa) production in North Carolina. This study was aimed at evaluating six summer cover crop treatments including pearl millet (Pennisetum glaucum), soybean (Glycine max), cowpea (Vigna unguiculata), pearl millet/soybean combination, pearl millet/cowpea combination, and a no cover crop control, with and without vermicompost additions for their effects on strawberry growth, yields, nutrient uptake, weeds, and soil inorganic nitrate-nitrogen and ammonium-nitrogen in a 2-year field experiment. Compost was additionally applied before seeding cover crops and preplant N fertilizer was reduced by 67% to account for organic N additions. Although all cover crops (with compost) increased soil N levels during strawberry growth compared with the no cover crop treatment, cover crops did not impact strawberry yields in the first year of the study. In the 2nd year, pearl millet cover crop treatments reduced total and marketable strawberry yields, and soybean treatments reduced marketable strawberry yields when compared with the no cover crop treatment, whereas vermicompost additions increased strawberry biomass and yields. Results from this study suggest that vermicompost additions can be important sustainable soil management strategies for transitional and certified organic strawberry production. Summer cover crops integrated with composts can provide considerable soil N, reducing fertilizer needs, but have variable responses on strawberry depending on the specific cover crop species or combination. Moreover, these practices are suitable for both organic and conventional strawberry growers and will benefit from longer-term studies that assess these practices individually and in combination and other benefits in addition to yields.