Book Description

A 0.4 ha planting of blueberry (Vaccinium corymbosum L.) was established in Oct. 2006 to evaluate the effects of cultivar (Duke and Liberty), planting method (flat versus raised beds), weed management (sawdust mulch and hand-weed control; compost plus sawdust mulch with acetic acid, flaming, and hand-weeding used as needed; and weed mat plus hand-weeding as needed), and type and rate of fertilizer (feather meal and liquid fish emulsion at 29 and 57 kg·ha−1 N) on plant growth, yield, fruit quality, irrigation requirements, and weed presence. The site was certified organic in 2008. Plants grown on raised beds were larger than on flat ground. The leaf nitrogen concentration (%N) in all treatments ranged from slightly below normal to slightly above normal in Aug. 2007 and Aug. 2008, depending on fertilizer treatment and mulch. Plants receiving 57 kg of N·ha−1 as fish emulsion had the highest leaf %N in both years, especially when grown with weed mat mulch, while plants fertilized with the low rate of feather meal had lower than recommended %N, especially in sawdust mulched plots. In Oct. 2007, total plant dry weight (DW) was higher in 'Liberty' than 'Duke', raised beds than flat ground, and when fertilized with fish emulsion rather than feather meal, but was not affected by weed management system. Root DW was greatest in 'Duke' and lowest in plants receiving 57 kg of N·ha−1 as fish emulsion when grown with weed mat. In Oct. 2008, treatment effects on total plant DW were similar to what was observed in 2007. Root DW in 'Duke' was not affected by planting on raised beds, but was greater in plants grown with the organic mulches and fertilized with 29 kg of N·ha−1 of fish emulsion. In 'Liberty', the greatest root DW was in plants with compost plus sawdust mulch and fertilized with 29 kg of N·ha−1 of fish emulsion, while leaf area was greatest in plants grown on raised beds with sawdust mulch and fertilized with 57 kg of N·ha−1 of fish emulsion. In 2008, yield was highest when 29 kg·ha−1 N of fish was applied and when plants were grown on raised beds with weed mat in 'Duke' (0.56 kg·plant−1), and with compost plus sawdust in 'Liberty' (0.57 kg·plant−1). Fruit were firmer at harvest when plants were fertilized with fish rather than feather meal and when soil was mulched with sawdust compared to weed mat. Weed presence increased from 2007 to 2008. Hand-weeding was required in all treatments in both years. Weed mat plots had the fewest weeds, whereas compost plus sawdust mulched plots had the highest weed coverage. In weed mat plots, the only weeds that emerged were in the area of the planting hole. In the compost plus sawdust mulched treatment, acetic acid applied at a 20% concentration on hot days, provided acceptable control of annual weeds, but was moderately effective on perennial weeds. Flaming was somewhat effective when used on small weeds on hot days. Soil water content was lower through the growing season on raised beds than on flat ground, especially under weed mat; this system thus required 148% more irrigation water than did plots mulched with sawdust, and compost plus sawdust to maintain an adequate percent soil water content for blueberry plant growth. Soil temperature at 5 cm depth was higher under weed mat and more variable through the year than in the organic mulched treatments. The extra irrigation water required in weed mat mulched treatments may have been associated with increased soil temperatures and soil water evaporation, and greater plant evapotranspiration. The organic production systems studied produced typical plant growth and yield, as compared to conventional production systems.