Effects of the Incorporation of Phosphorus and Iron into Arsenic-Spiked Artificial Soils on Root Growth of Lettuce using Response Surface Methodology

We investigated effects of phosphorus (P) and iron (Fe) on root elongation (RE) of lettuce in arsenic (As)–spiked soils using response surface methodology (RSM). To stabilize interactions between As and Fe in a soil preparation, the sequential incorporation method using Fe and P (SIM_Fe-P) was applied. From a phytotoxicity assay, As in roots (As_root) was negatively associated with RE, Fe in soils, and P in roots and soils. The P in roots was also positively related to RE. In a model study, As and interaction factor between P and Fe showed negative coefficients but others showed positive ones. From a confirmation study, RE on exposure to As was verified to be much greater in soils treated by SIM_Fe-P than in soils separately treated with both elements. These results indicated that application of SIM_Fe-P to As-contaminated soils might be expected to have an advantage during the early stage of plant root growth.