Comparison of soil pH, electrical conductivity, and concentrations of essential minerals and toxic trace elements in paddy fields across different provinces of Sri Lanka

To support effective decision-making, this study aimed to assess the variation in soil fertility across lowland paddy fields in different administrative provinces of Sri Lanka by analyzing soil pH, electrical conductivity (EC), essential mineral elements, and toxic trace element concentrations. A total of 1,024 paddy soil samples representing nine provinces were collected using a stratified random sampling approach. Exchangeable element concentrations in soils were extracted using 0.01 M CaCl₂ and were measured using Inductively Coupled Plasma Mass Spectrophotometry (ICP-MS). Soil pH and EC were measured using the 1:5 soil: water extraction method. Northern, Northcentral, and Southern provinces reported the highest soil pH while Sabaragamuwa and Western provinces reported the lowest. Electrical conductivity was similar among provinces. Exchangeable Mg, K, and Ca were the lowest in Central and Sabaragamuwa provinces. Central, North-western, Northern, and North-central provinces had the lowest exchangeable Zn, Mo, Ni, Cu, and Al concentrations. Southern and Western provinces had the lowest Na, Co, and Mn concentrations. Exchangeable As, Cd and Pb were higher in Western and Sabaragamuwa provinces than in other provinces. Exchangeable Na, Mg, K, Fe, and Mo had positive relationships with soil pH and EC while exchangeable Al, Co, Zn, and Cd had negative relationships with soil pH. This information is valuable for managing and enhancing the fertilit