Soil pH and the Foliar Macronutrient/Micronutrient Balance of Green and Interveinally Chlorotic Pin Oaks

Abstract

Soil pH values around chlorotic pin oaks and green pin oaks were significantly different to a depth of 55 cm. Throughout that depth, average values around green trees were 6.1–6.8; those around chlorotic trees averaged 7.2–7.4 and were within a total range of 6.7–7.9. Mean foliar concentrations of Fe, Mn, and Zn were each significantly lower in chlorotic tree foliage for at least 1 of the 3 seasonal sampling periods. Mean concentrations of P, K, and Mg were each significantly higher in chlorotic tree foliage for at least 1 of the 3 sampling periods. Eighty-six percent of all chlorotic tree samples (159) could be distinguished from all green tree samples (124) either by lower micronutrient concentrations or higher macronutrient/micronutrient ratios. As treated trees progressed from a chlorotic to a totally green condition, each underwent reductions in foliar N and P concentrations. Green trees fertilized with ammonium phosphate had significantly lower concentrations of Fe, Cu, and K + Ca + Mg concurrent with significantly higher concentrations of N and P when compared to the controls. It is concluded that chlorotic pin oaks should not be deemed as simply iron-deficient and that indiscriminant fertilization of pin oaks or the lawns around them with NPK fertilizers may be deleterious.