Effect of rate and source of nitrogen fertilizers on mineral composition of d'Anjou pears

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Abstract
Thirteen‐year‐old ‘d'Anjou’ pear trees, Pyrus communis L., were fertilized with 3 rates of ammonium nitrate or 2 rates of calcium nitrate in late autumn from 1978 to 1980. In 1981, mid‐terminal and fruiting‐spur leaves and fruit peel and flesh were sampled for mineral analysis of N, P, K, Ca, Mg, B, Cu, Fe, Mn, and Zn. The level of N increased in the above tissues as rate of N fertilizer was increased. In most cases, the levels of N, P, K, Mg, Cu, and Mn in the fruiting spur leaves and fruit were greater in the ammonium nitrate‐treated trees than with calcium nitrate fertilizer. Calcium was higher in the fruit peel and flesh of trees treated with the low rate of calcium nitrate than with the highest rate of ammonium nitrate fertilizer while Ca in the fruiting spur leaves was lower in the calcium nitrate‐fertilized trees.