Organic production systems in northern highbush blueberry: II. Impact of planting method, cultivar, fertilizer, and mulch on leaf and soil nutrient concentrations and relationships with yield from planting through maturity

Authors: STRIK, BERNADINE - Oregon State University; VANCE, AMANDA - Oregon State University; Bryla, David; SULLIVAN, DAN - Oregon State University

Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/19/2019
Publication Date: 10/4/2019
Citation: Strik, B.C., Vance, A., Bryla, D.R., Sullivan, D.M. 2019. Organic production systems in northern highbush blueberry: II. Impact of planting method, cultivar, fertilizer, and mulch on leaf and soil nutrient concentrations and relationships with yield from planting through maturity. HortScience. 54(10):1777-1794. https://doi.org/10.21273/HORTSCI14197-19.
DOI: https://doi.org/10.21273/HORTSCI14197-19

Interpretive Summary: Consumer demand for organic blueberries is increasing rapidly in United States, but information on how to grow the crop is limited. To address this issue, various production systems were tested from planting to maturity in a long-term certified organic trial. The results indicated that establishing blueberry plants on raised beds rather than flat ground was critical for maximizing plant growth and yield. Choice of a mulch was also important, both economically and for weed control. Weed mat was the most economical method of controlling weeds and increased yield by as much as 11% over the conventional use of sawdust mulch. However, weed mat resulted in problems with rodents (voles) in the planting and reduced soil organic matter content, which may be of concern for longer-term production. To compensate, many growers use compost, but regular use of compost added considerable weed management costs and increased potassium to levels that were potentially toxic to the plants. Fertilization with fish solubles, which is commonly used, also led to higher levels of potassium in the plants and decreased yield in certain cultivars. Feather meal was a suitable alternative to fish solubles and had a positive effect on calcium in the fruit and plants. Growers are currently using this information to manage their plantings and improve organic production of blueberries.

Technical Abstract: The impact of various production systems on leaf and soil nutrients was evaluated for 10 years in a certified organic planting of northern highbush blueberry. Treatments included two cultivars (Duke and Liberty), flat and raised planting beds, low and high rates of fertilization with feather meal or fish solubles, and three types of mulch (sawdust, compost topped with sawdust, or weed mat). On average, raised beds resulted in higher concentrations of nitrogen (N), phosphorus (P), potassium (K), and iron (Fe) and lower concentrations of calcium (Ca), magnesium (Mg), and boron (B) in the leaves than planting on flat ground, while fish solubles resulted higher concentrations of N, P, and K and lower concentrations of Ca in the leaves than feather meal. Use of compost in the mulch increased organic matter content and the concentration of P, K, Ca, and Mg in the soil relative to the other mulches and resulted in higher concentration of K in the leaves in both cultivars. Concentration of Ca in leaves, on the other hand, was highest with sawdust and lowest with weed mat. In ‘Duke’, yield was positively correlated with the concentration of Ca in the leaves during 8 out of 9 years of fruit production and was negatively correlated with the concentration of P and K in the leaves in 5 and 6 years, respectively. Concentration of Ca and Mg in the leaves was also negatively correlated with K in the leaves in most years. The results suggest that soil nutrient imbalances and changes in leaf nutrient concentrations associated with extended use of compost and fish solubles may lead to growth and yield problems in longer-lived plantings.