The salinity of motorway soils. IV. Effects of sodium chloride on some native British shrub species, and the possibility of establishing shrubs on the central reserves of motorways.
Individuals of eleven native British shrub species growing in containers out of doors were subjected to sodium chloride solutions of different concentrations, either periodically sprayed on to the plants, or added to the soil, through two successive winters (1977-79). newline˜Salt solutions added to the soil produced concentrations per unit dry weight of soil of up to 2500 μg N g-1 and 1500 μg Cl g-1 by the start of the growing season. In general, solutions added to the soil had greater effects than the same solutions sprayed on to the plants. There was considerable difference among species in the concentrations in the soil that caused a given mortality or reduction of growth. Susceptibility to salt spray damage was not closely correlated with susceptibility to salt damage via the soil. newline˜From a knowledge of sodium and chloride concentrations in the soil it is concluded that in the southern half of England many species of shrub could be grown in the central reserves of motorways, but that few could be grown in this situation in the north and probably none in the extreme north-east. Circumstantial evidence to support this conclusion is reviewed.