Magnesium relationships in soils and plants

Abstract

Abstract Most of the magnesium, in British soils is contained in micas, chlorites and vermiculites in the clay minerals. The exchangeable‐solution forms, from which plants obtain their magnesium, are replenished by decomposition of the silicate minerals. Laboratory studies suggest that the nature, composition, and particle size of the magnesium minerals, and the acidity and temperature of the soil will all affect the rate at which silicate magnesium is released. The combined losses of magnesium by leaching and crop removal may be IO‐50 Ib. of Mg/acre, which could be replenished by the release of only a small fraction of the total silicate magnesium. Apart from possible additions by manurial treatments, some magnesium is also supplied in rain. Magnesium deficiencies in crops are caused not only by inadequate exchangeable‐solution magnesium, but also by ion antagonisms in acid soils and soils rich in potassium. Present methods of assessing the available magnesium in soils do not take account of these effects.