Impact of soil-type, soil-pH, and soil-metal (loids) on grain-As and Cd accumulation in Malawian rice grown in three regions of Malawi
Angstone Thembachako Mlangeni, Shaun T. Lancaster, Andrea Raab, Eva M. Krupp, Gareth J. Norton, Jörg Feldmann
Abstract
Impact of soil type, soil-metal(loids) and soil-pH of rice paddies on grain-arsenic (As) and cadmium (Cd) accumulation in Malawian rice was investigated to explore the extent to which Malawi's geographical location, soil types, soil-metal(loids) and soil-pH and their interactions impact on grain-As and Cd accumulation. Multivariate techniques were used to evaluate the relationships among measured parameters. Results showed that the 1st three principal components consisting of soil-types, soil-metal(loids) and soil-pH explained 83% of total variance of both grain-As and Cd accumulation. For As, highest grain-As was detected in rice from central region (CR) cultivated in vertisols characterized with soil-As ≥ 2.5 mg/kg and soil-pH > 7.0 whereas the lowest was in rice from northern region (NR) cultivated in fluvisols characterized with soil-[As] ≤ 1.5 mg As/kg soil and soil-pH range of 6.00–6.99. For Cd, highest grain-Cd was detected in rice from CR cultivated in luvisols with soil-As range of 2.0–3.0 mg/kg and soil-pH < 6.0. For correlation, highest significant correlation coefficient was between soil-As and grain-As (0.512; p < 0.001); and soil-pH and soil-As (0.545; p < 0.001) while correlation coefficient between soil-Cd and grain-Cd and soil-Cd and grain-As were weaker and/or non-significant. These results indicate a synergy impact of soil type, soil-pH, and soil-metal(loids) that simultaneously influence low grain-As and Cd accumulation.