2019 ASHS Annual Conference

Acidic soils with high organic matter content are recommended for optimal blueberry growth. However, blueberry production east of the Cascade Range in the Washington State utilizes native soils that are naturally high in pH, have high free calcium carbonate content, and are low in organic matter. These edaphic factors affect nutrient cycling and availability, which ultimately affects plant growth and development. Even though growers have historically amended the soil to lower pH, few studies have been conducted on organic blueberry nutrient management in this economically important region. Growers need additional recommendations so they can optimize nutrient management and the long-term productivity of their plantings. The overall objective of this study was to evaluate the impacts of different commercially available organic nitrogen (N) sources and rates in organic blueberry grown in eastern Washington soils and measure treatment effects on plant growth, yield, and fruit quality. Four commercially available organic N fertilizer treatments and three rates were evaluated in a field established as a split plot randomized complete block design using ‘Duke’ blueberry. Fertilizer source treatments include: 1) Blood meal (14-0-0); 2) TRUE 402 fish emulsion (4-0-2); 3) WISErg (3-2-2) derived from digested plant materials; and 4) Combination (40% blood meal and 60% WISErg). Fertilizer rate was split within source at 57, 112, and 168 kg·ha^-1 N. Yield, fruit quality, vegetative growth, and leaf nutrient concentrations were measured in 2018. Overall, TRUE 402 applied at 57 kg·ha^-1 had the highest yield compared to any other fertilizer treatment whereas WISErg applied at 168 kg·ha^-1 had the lowest yield. Higher rates of fertilizer tended to encourage greater shoot growth and lower yields. No significant difference was observed in N leaf concentration among the treatments. Fruit quality variables such as berry mass, firmness, ˚Brix, and Titrable Acidity (TA) were unaffected by the treatments. This study is in progress and will continue to be monitored in 2019.