Acid Sulphate Soils: Characteristics, Constraints and Integrated Management Strategies for Sustainable Utilization

Abstract

Acid sulphate soils, rich in iron sulfides such as pyrite (FeS₂), are highly acidic soils that severely limit agricultural productivity due to low pH, aluminium and iron toxicity, nutrient imbalances, and poor fertility. In Kerala’s Kuttanad region, these soils pose major constraints to rice-based cropping systems. Acid sulphate soils(ASS) exhibit high potential acidity, variable organic carbon content, and microbial communities dominated by sulphur-oxidising bacteria, leading to sulphuric acid formation upon pyrite oxidation. Effective management requires integrated strategies, including avoidance of soil disturbance, neutralisation with lime and silicate amendments, enhancement of soil organic matter, nutrient management with organic and inorganic inputs, biological interventions such as sulphate-reducing bacteria, and water management through reflooding, groundwater manipulation, and tidal buffering. Cropping system interventions, including rice-fish rotational farming and raised bed cultivation of cassava and vegetables, alongside Al- and Fe-tolerant rice varieties, further improve productivity. These combined approaches mitigate acidity and metal toxicity, enhance nutrient availability, and maintain soil organic carbon, enabling sustainable utilization of ASS in challenging coastal wetland ecosystems.