Calcium as an environmental variable
Abstract. The chemical state of calcium in the soil and the effects, both direct and indirect, which this can have on the growth and distribution of plants are considered. Recent advances in knowledge refer mainy to interactions (between nitrogen source, aluminium and pH, for example) for which there is now experimental evidence and which themselves are influenced by calcium. The impact of physical variables is less marked than first thought although seasonal effects of waterlogging and drought can be critical. It is emphasized that the terms ‘calcicole’ and ‘calcifuge’ are generally acceptable in classifying plants according to the degree of calcareousness of the soils in which they occur but only if the wider implications are appreciated.