Climatic control of major and trace elements in paddy soils from wet and dry regions of Sri Lanka

Abstract

Rice cultivation is a widespread agricultural practice in the dry and wet climatic zones of Sri Lanka. Due to the excessive application of agrochemicals, paddy soils are considered to be polluted, particularly with toxic trace elements. To assess the major and trace element levels in rice paddy soils, 97 samples were collected from the main two climatic regions of Sri Lanka. Total and exchangeable contents of 12 major and trace elements, i.e., Na, K, Ca Mg, Fe, Mn, Cr, Ni, Zn, Pb, Cu, and As were analyzed. Geo-accumulation index and Potential Bioavailability Factor (PBF) was employed to assess the levels of contaminations and results were statistically compared. Paddy soils from both climatic zones contained over 5.0 mg/kg of available–P, which is almost equal to the optimum levels required for rice plants. The total content of trace metals varied in the order Fe>Mn>Zn>Cu>Ni>As in both dry and wet zones, while major elements increased in the order Mg>K>Na. Geo Accumulation indices (Igeo) showed that almost all soils were uncontaminated to moderately contaminated with trace elements.

Keywords

• Geo-accumulation index
• Trace elements
• Fertilizer application
• Bioavailability factor
• Exchangeable fraction