Effect of fertilizers on soil pH and performance of apple and pear trees. II. Grown in different soils in the orchard

Abstract

In the apple orchard, trees fertilized with calcium nitrate resulted in the highest soil pH (6.4) whereas the lowest pH (4.7 and 4.6) occurred with ammonium nitrate and with mono‐ammonium phosphate (MAP) applications, respectively. Soil pH values were lowest with the high rates of nitrogen (N) fertilizers. Red skin color of ‘Delicious’ apples was generally improved with calcium nitrate fertilization, higher soil pH values, and with lower fruit manganese (Mn) concentrations or with lower N fertilizer rates. Incidence of bitter pit was lowest for trees fertilized with ammonium nitrate or calcium nitrate. In the pear orchard, the lowest soil pH (4.2) occurred when trees were fertilized with the high rate of MAP and the highest soil pH (4.8) occurred with the high rate of calcium nitrate applications. Fruit size was slightly smaller on trees fertilized with the high rate of MAP. Lowest incidence of superficial cork or green stain fruit disorders occurred on trees receiving the high rate of calcium nitrate. Fruit quality and mineral nutrient composition of leaves and fruit were determined for apples and pears.