Calcium and magnesium fertilization in wild lowbush blueberry in Quebec

In recent years, wild lowbush blueberry (Vaccinium angustifolium Ait.) yields have increased steadily with the improvement of agricultural practices. However, this increase in productivity has reduced the foliar concentrations of calcium (Ca) and magnesium (Mg) under the minimum standard concentrations insuring optimal plant growth. Thus, the objectives of the study were to determine the impact of the application of Ca and Mg amendments on the blueberry productivity and on the soil physico-chemical properties. Four rates of Ca sulfate (0, 540, 1080 and 2160 kg ha-1) and Mg sulfate (0, 31.5, 63 and 94.5 kg ha-1) were applied in the spring of the sprout year. Soil pH increased significantly by 0.4 and 0.1 unit with Ca application in the soil layers 0-5 and 5-20 cm respectively. Significant Ca and Mg accumulations of 746 and 53 mg kg-1, respectively, were measured in the surface soil layer after amendment applications compared with the control. Increases of Ca were also found in the 20-40 cm layer indicating that Ca was partially leached. Leaf N, P, K and Ca concentrations increased significantly with the Ca application while Mg application increased leaf Mg concentration. Mean fruit yields reached 3042 kg ha-1 but were not significantly influenced by Ca and Mg application. Stem density was reduced with Mg application whereas the number of flower buds and stem length were not affected. Although Ca and Mg application resulted in significant increases in soil and leaf nutrient concentrations, this did not translate in blueberry yield improvement.