Abstract

The objective of this experiment was to evaluate the effect of four ammonium N rates on fruit yield and leaf nutrient concentration in blueberry (Vaccinium corymbosum) cultivars grown on a substrate. The experiment was conducted with increasing ammonium sulfate (NH4-N) rates 0, 100, 200, and 300%), using plants of two-year-old of pot-grown nine highbush blueberry cultivars, grown in 35 liters (L) pots with soilless media, consisting of coconut fiber, peat, and perlite at 2:2:1 (v/v). Leaf nutrient concentration was affected by cultivar and nitrogen (N) rate. Increasing the N rate increased N, P (phosphorus), Ca (calcium), Mg (magnesium), S (sulfur), and Mn (manganese) concentrations and decreased K (potassium), Cu (copper), and B (boron) concentrations in most cultivars. Increasing the N rate increased fruit yield per plant equivalent to 67%, 93%, and 152% concerning the control. Considering the highest fruit production obtained with NH4-N rates from 100% to 300% leaf nutrient concentrations (%) ranged from 1.83 to 2.82 for N, 0.10 to 0.15 for P, 0.62 to 1.04 for K, 0.31 to 0.63 for Ca, 0.13 to 0.24 for Mg, and 0.20 to 0.59 for S. The main conclusions obtained are: leaf N and S concentration responded positively to applied N, yield was almost always positively affected by N, and the reference standard for foliar analysis in blueberry should be adjusted according to the cultivar.