Fruit Quality and Nitrogen, Potassium, and Calcium Content of Apple as Influenced by Nitrate: Ammonium Ratios in Tree Nutrition.

Evaluations of fruit quality and nitrogen, potassium, and calcium concentration of apple (Malus domesticaBorkh. cvs. Gala and Golab) grown with five treatments of NO3−:NH4+ratios were made in pot culture. The concentrations of NO3−:NH4+ratios were 2.5:0.1, 6:1, 6:0.7, 6:0.5, 6:0.3 meq L−1. Fruit size, percent dry matter, total dissolved solids, total acidity, or juice pH was not affected by increased ammonium in the ratio. Firmness decreased as the proportion of NH4+increased. Gala and Golab differed in some of these parameters. Concentrations of N and K increased as NH4+increased, whereas Ca had no trend or decreased. Generally, the treatment of 2.5:0.1 produced fruits with lower N but higher K and Ca concentrations than the other treatments. This research showed that some parameters such as fruit weight, length, and diameter, juice pH, and dry matter were not affected significantly by NH4+concentration whereas composition was affected. [ABSTRACT FROM PUBLISHER]