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.