Organic farming systems increase anthocyanin and vitamin C content of rabbiteye blueberry (Vaccinium ashei Reade 'Tifblue') on a heavy soil

Increased concerns over the last several decades on environmental problems have stimulated farmers to accept organic farming as an alternative to inorganic agriculture. Blueberries are one of the richest sources of antioxidant phytochemicals having a high level of anthocyanins. Anthocyanins are phenolic compounds that possess antioxidant activities. Rabbiteye blueberry (Vaccinium ashei Reade 'Tifblue') was grown on Memphis Silt Loam soil (Typic Hapludalf, silty, mixed, thermic) with another cultivar, 'Powderblue', for cross pollination. Two organic manure treatments (worm castings, cow manure) were applied in basins around each plant. The control treatment received regular inorganic fertilizer. All treatments received pine bark and pine needle mulch uniformly. No chemicals were applied to control pests, diseases, and weeds. Percent canopy cover, LAI, canopy width and height, stem diameter, and yield were significantly higher in organic plants treated with worm castings. There was no significant difference in size, diameter, and degree brix of the fruit, but the content of vitamin C was higher in fruit treated with worm castings. There was no difference in microbial load and no pathogens were found in the fruit. Concentrations of nitrate-N and P were higher in surface soils treated with organic manures, but there was no trend in N or P enrichment in lower layers of the soil. The leaching of N and P into subsurface layers from inorganic fertilizer was highly significant. Blueberry can be grown successfully on heavy soils with forest waste that can maintain soil structure and acidity, and worm castings and cow manure improve yield and fruit quality of this crop.