2017 ASHS Annual Conference

In Washington state, blueberry is grown in two very climatologically and geographically different regions. Western Washington is characterized by high precipitation and mild temperatures whereas east of the Cascade Mountains, in central Washington, there is low precipitation (ca. 150 mm/year) and cold winters with warm to hot summers. Soils in western Washington are also naturally acidic, while eastern Washington soils are alkaline and must be substantially amended to reach a suitable pH range for blueberry production. Our ongoing research is evaluating differences in leaf tissue nutrient concentrations in these two regions to establish guidelines for growers to use for nutrient management. Growers often are not certain what the best location is within the canopy or on a branch for tissue nutrient sampling, which could impact a growers’ assessment of a nutrient management program if tissue nutrient concentrations vary based on canopy or branch position. To answer this question, we intensively sampled leaf tissues from ‘Draper’ blueberries in late July/early August from three western and two central Washington fields. Leaves were collected from the top, middle and lower portions of the canopy using three different leaf positions at each canopy location (youngest fully mature leaf, leaf subtending the fruiting cluster, and low branch position [old/most mature] leaf). These sampling positions were replicated three times in each field. The results showed that tissue nutrient concentration differed by growing location but was not affected by branch position. However, the concentrations of eight nutrients (nitrogen, phosphorus, potassium, magnesium, sulfur, copper, manganese, and zinc) differed by canopy position, where the nutrient concentrations were highest in the lower portion of the canopy and lowest in the upper portion. The results suggest that the middle portion of the canopy should be consistently used for sampling and subsequent evaluation of a nutrient management program, but that samples can be taken from random branch positions.