Positive and negative impacts of plants on acid production in exposed acid sulphate soils

Abstract

This study examined the impact of plants on acid sulphate soils with the aim of determining whether plants are able to reduce acid production. The study was conducted with clayey acid sulphate soil under controlled conditions with treatments lasting up to 24 weeks and measurements made in the top 0–60 mm of soil. pH profiles in the soil were strongly dependent on soil moisture and the pattern of irrigation. When bare soil was allowed to dry down without further irrigation, there was very little acidification of either the surface or subsurface layers. Planting of Phragmites accelerated soil drying and caused extensive cracking and acidification of the subsoil under simulated drought conditions. Under a wetting and drying regime, both Phragmites and a surface spreading grass Paspalum increased soil acidification, while a surface spreading herbaceous shrub Cotula had little effect on acidification. There was no evidence that live plants could ameliorate acid sulphate soils. However, application of dead plant matter to the surface of the soil was effective in reducing acidification, especially if submerged.Robert J. Reid and Christopher S. Butche