Magnesium deficiency in chestnut: the influence of soil manganese

Abstract

A regional survey was carried out in chestnut groves established in soils derived from bedrock of several geological formations, some with materials rich in manganese (Mn). A total of 38 chestnut groves were selected: 19 groves with several trees showing symptoms of Mg deficiency and 19 groves in their vicinity with vigorous tree growth. Foliar nutrient concentrations and several soil fertility indicators were determined.

The lowest value of leaf Mg concentration in good growing conditions was 1.8 g kg^-1 and the highest value in trees with evident symptoms of Mg deficiency was 1.5 g kg^-1. In the majority of chlorotic groves, soil exchangeable Mg was below 0.20 cmolc kg^-1. But the soils with Mn higher than 25 mg kg^-1 exhibit symptoms of Mg deficiency up to 0.33 cmolc kg^-1 of exchangeable Mg. In soils with the highest contents of Mn (>200 mg kg^-1) the chestnut groves were established on Mn-rich schists and greywackes of the Ordovician and the Silurian.