Soils were collected from a number of community types including semi-natural grassland, scrub, woodland, arable fields and improved grassland on various parent substrates and their fertility assessed by chemical analysis and plant bioassay techniques. Under glasshouse conditions, the main limiting factor to plant growth on the soil collected was the availability of P. Levels of extractable P in the arable soils, improved grassland soils and in some of the scrub and woodland soils collected were found to be significantly higher than in adjacent, semi-natural grassland soils. It may therefore be necessary to reduce the availability of P in the soil before species-rich grassland can be successfully established and maintained on old field sites produced by 'set-aside' or extensification schemes, and in conservation management programmes where late successional vegetation is removed. © 1990.