Effect of Phosphorus or Silicon on the Arsenic Content of Japanese Mustard Spinach (Brassica rapa var. perviridis) Grown on Arsenic Contaminated Soil

Two experiments were conducted about the effect of the application of phosphorus (P) or silicon (Si) on the arsenic (As) contents of Japanese mustard spinach (JMS) (Brassica rapa var. perviridis) grown on As contaminated soil (30.6 mg As kg-1). The P was applied with four different P fertilizers derived from both organic or inorganic sources viz. chicken manure (CM), bone powder (BP), fused magnesium phosphate (FMP), and super phosphate (SP). The P was applied at two rates (50 and 100 kg citrate soluble P2O5 ha-1). The As contents (mg kg-1 dry weight [DW] and/or µg plant-1) in the edible part of JMS reduced significantly as compared to the As contents in control plant with the application of P, irrespective of the form of fertilizer and to the application rate of P. There was no significant difference among the P fertilizers as well as the rate of P application in reducing As contents in the plant. The growth of the plant and P concentration in the plant part increased significantly with the application of P. In the Si application experiment, Si was applied from three different sources viz. potassium silicate (PS), magnesium trisilicate pentahydrate (MTP) and lherzolite (LE). Silicon was applied at the rate of 1,050 kg SiO2 ha-1. The As contents in the edible part of JMS increased, but not significantly, as compared to the As contents in control plant with the application of Si irrespective of the source of Si. There was no significant difference in the As contents in the edible part of the plant among the Si sources. The magnesium content in the plant part was increased significantly with the application of MTP and LE. The growth of the plant and the other mineral concentrations in the plant part was statistically similar as compared to the control plant. The results of two experiments indicated that the application of P could reduce the As contents in the edible part of JMS whereas Si had no effect to reduce As content in JMS under the employed condition.