The Effects of the Incorporation of Phosphorus and Iron Into Arsenic-Spiked Artificial Soils On the Root Growth of Lettuce (Lactuca sativa L.) Using the Response Surface Methodology.

The aim of this study was to assess the effects of phosphorus (P) and iron (Fe) on the root elongation (RE) of lettuce in arsenic (As)-spiked soils, using the response surface methodology (RSM). To stabilize the interaction between As and Fe in a soil preparation, the sequential incorporation method between 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 (P_root and P_soil); whereas, As in soils (As_soil) showed a positive relationship with As_root. P_root was also positively related to both P_soil and RE. In a model study, only the linear and interaction factors were observed to be significant. As and interaction factor between P and Fe showed negative coefficients but others showed positive. Especially, P, As, and interaction factor between As and Fe (As*Fe) showed higher explanations of the response (> 14%). These results indicated that although As in soils inhibited RE, P and As*Fe positively affect. 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 the two elements. Although the ranges of the soil parameters and test soils studied were limited, the application of SIM_Fe-P to As-contaminated soils might be expected to have an advantage during the early-stage of plant root growth. Also, the approaches from RSM might be considered to be suitable for interpreting the interactions between many factors in soils.