Location: Horticultural Crops Research2013 Annual Report
1a. Objectives (from AD-416):
1) Evaluate blueberry plant growth, yield, and quality in various certified-organic production systems in two popular fresh-market cultivars; 2) determine the effect of raised beds on soil and plant water status and plant growth, and production; 3) evaluate and continue to develop organic weed management systems in producing blueberries; and 4) develop and evaluate organic fertilizer treatments to optimize plant growth, production, and quality.
1b. Approach (from AD-416):
Treatments being assessed include planting on raised beds or flat ground, various weed management treatments including weed mat, organic fertilization type and rate, and cultivar. We will collect information on not only the effectiveness of the treatments such as weed mat, sawdust and compost mulches and use of vinegar for weed control on flat ground and raised beds and organic fertilizers and how they interact with sawdust mulch and weed mat, but also the cost effectiveness. We will measure plant growth, yield, fruit quality, weed pressure, soil water status, plant water status, plant tissue and soil nutrient concentration, and organic fertilizer availability. We will make observations on any other pest problems and control them to the best of our ability using organically approved methods. We feel that this study will provide growers with very useful information on the long-term impacts and costs of various organic blueberry production systems during fruiting years. Documents Grant with Oregon State University. Formerly 5358-21000-037-16G.
3. Progress Report:
This research was conducted in support of NP 305 objective 1 "Determine nutrient requirements to enhance product quality in woody perennial crops such as grapevine and rhododendron" of the parent project. A long-term systems trial was established to evaluate management practices for organic production of northern highbush blueberry (Vaccinium corymbosum L.). The factorial experiment included two planting bed treatments (flat and raised beds), source and rate of fertilizer (feather meal and fish emulsion applied separately at a low, 29–57 kg•ha-1 N, or high rate, 57–102 kg•ha-1 N, depending on planting age), weed management (sawdust mulch, compost topped with sawdust mulch, or weed mat), and cultivar (‘Duke’ and ‘Liberty’). The planting was established in Oct. 2006 and was certified organic in 2008. Cumulative yield, over five fruiting seasons (2008-2012) was 23% higher on raised beds than on flat ground. ‘Duke’ plants fertilized with feather meal had greater yield than those fertilized with fish emulsion, but yield of ‘Liberty’ was not affected by the source or rate of fertilizer applied. In both cultivars, fertilization with the high rate of fish emulsion increased fruit firmness and percent soluble solids compared to the low rate of fish emulsion or the use of feather meal. High rates of fertilizer, particularly with fish emulsion, have reduced soil pH over time and have increased leaf nitrogen content (%N) in most years. None of the leaf nutrient concentrations, however, including %N, were correlated to yield. Weed mat was the best option for weed management, while yard debris compost plus sawdust mulch resulted in the most weeds and the highest weed-control cost; yield however was similar between the two treatments and higher in three out of five years than when using sawdust mulch alone. Effects of mulch type on fruit quality were inconsistent over the length of the study. Plants mulched with weed mat required additional irrigation to maintain the same soil water content as those mulched with sawdust or compost plus sawdust, especially when grown on raised beds. Soil organic matter content declined under weed mat and increased under the compost plus sawdust mulch over the length of the study. Soil potassium content increased when using compost plus sawdust mulch. Growth and yield of the “best” treatment combinations have been similar to well-managed conventional production systems.