Effect of commercial calcium-boron and manganese-zinc formulations on fruit set of cranberries

SummaryIn a 3-year field experiment, commercial foliar fertilizers containing Ca and B or Mn and Zn were hand-sprayed on cranberries. They were applied during a period of low foliar levels of Ca and Mn which occurs during a time of strong vegetative growth and floral development. The yields (3-year average) for areas treated with CaB were increased in nine of ten application combinations for the cv Early Black, and in all ten application combinations for the cv Howes, due to increased fruit set. The most effective treatment date combination was the first week of June and the first week of July (full bloom). This combination gave yield increases of 45% (Early Black) and 68% (Howes). The MnZn treatments did not significantly affect yield, but they did negate the beneficial effect of the CaB material on fruit set. The CaB experiments were repeated on a large scale using aircraft and sprinkler applications. Aerial split applications resulted in 24-31% yield increases, and a single application (bloom) resulted in 17-19% increases. Sprinkler applications, split and single (bloom), were less effective (average increase 20%). At the greatest distance from the source pump, little or no effect of the sprinkler application was recognizable.