The Effect of Different Methods of Fertilization with Ammonium Sulfate and Urea on Yield and Fruit Size of Highbush Blueberry ( Vaccinium corymbosum L.)

Abstract The objective of this study was to evaluate the effects of liquid fertilization through drip irrigation with nitrogenous (N) fertilizers, including ammonium sulfate and urea, compared to the application of granular fertilizers on highbush blueberry plants (Vaccinium corymbosum L.) cultivar 'Draper' during the first three years of fruit production (2020–2022). Planting of the saplings took place in April 2018, distance were 1.1 m within rows and 2.8 m between rows 3246 shrubs/ ha. Control variants (no fertilization) were identical for both fertilization methods (liquid and granular). The substrate was a mixture of soil, peat, and pine bark in a 1:1:1 ratio. Both types of fertilizers were used at three N rates, which were increased each year as the plants entered into production (70 to 95, 135 to 190, 195 to 270 kg/ha N). In the first year with liquid fertilization, the yield was 3.8 t/ha, while with granular fertilization, it was 2.7 t/ha, indicating a 29% higher yield with liquid fertilization. Additionally, the yield was 14.8% higher with ammonium sulfate compared to urea. The nitrogen concentration in the leaves with liquid fertilization reached 1.78%, while with granular fertilization, it was 1.67%. Moreover, with ammonium sulfate, it was 1.89%, and with urea, it was 1.73%. Overall, the highest total yield ranging from 16.9 to 25.9 t/ha during the first three years of production was achieved when plants were fertilized with ammonium sulfate or urea at an annual rate of 70–95 kg/ha N. Our research found that liquid fertilization is more efficient in maximizing yield and optimizing the amount of nutrients.Liquid fertilizers evenly distributed using drip irrigation, this uniform application helps ensure that all plants receive the same amount of nutriens.