Comparison of Split or Single Application of Gypsum for Wild Lowbush Blueberry (Vaccinium angustifolium Ait.)

Gypsum (CaSO4·2H2O) was evaluated as a single pre-emergent application (4,482 kg/ha) or a split application (2,242 kg/ha pre-emergent and 2,242 kg/ha 2 weeks later) for its effect on soil nutrient release, nutrient uptake, and plant growth at two commercial lowbush blueberry fields (Clary Hill and Marshville, Maine). Gypsum applications were compared to diammonium phosphate (448 kg/ha) and a control using 0.9 m × 15 m plots arranged in a randomized complete block design with six blocks. Composite leaf and soil samples were collected within each treatment plot in July 2009 and analyzed for nutrient concentrations. Within each treatment plot, stems from four randomly placed 0.023 m2 quadrats were collected in October 2009 for stem length, branching, and flower bud measurements. Gypsum raised soil Ca and S concentrations at both fields compared to diammonium phosphate and the control. One of the fields (Marshville) was deficient in leaf N and P. Diammonium phosphate raised leaf N and P concentrations compare...