Chemical amelioration of high phosphorus availability in soil to aid the restoration of species-rich grassland

Abstract

Whilst removal of phosphorus (P) by vegetation harvest can take decades to reduce plant-available soil P significantly, chemical amelioration offers a possible method of reducing P availability more rapidly by immobilizing P in a form unavailable for plant uptake. A replicated block experiment was established on two field sites using treatments of aluminium sulphate, elemental sulphur (S) and calcium carbonate to investigate the possibility of reducing P availability. Five plant species typical of wet grasslands were transplanted into the treated soil to investigate the effect of the treatments on species diversity. The results show that P availability in 0.15 m topsoil was significantly reduced by aluminium sulphate initially by 47% at site 1 and by 33% at site 2, with the effect persisting for the 15-month experimental period. P availability was increased at site 2 by the high dose elemental S treatment by 11%. Site 1 showed a similar trend in the S treatment but the trend was not significant. P availability was not affected by the calcium carbonate treatment. Botanical diversity was not increased by any of the treatments and was initially decreased by the aluminium sulphate treatment at both sites. This could have been due to the associated reduction in pH, which favored the dominant species, Holcus lanatus.