Sparingly-Soluble Phosphate Rock Induced Significant Plant Growth and Arsenic Uptake by <i>Pteris vittata</i> from Three Contaminated Soils

We evaluated the ability of As-hyperaccumulator <i>Pteris vittata</i> (PV) to remove As from As-contaminated soils over five harvests in 2.5 years in raised beds (162 kg soil/bed). We tested the hypothesis that a P-limiting environment would enhance PV growth and As uptake owing its unique ability to uptake P under As-rich environment. In Dec. 2009, PV was transplanted to three As-contaminated soils (pH of 5.5–7.2) containing 25–129 mg kg^–1 As, which was amended with sparingly-soluble phosphate rock (PR-soil) or soluble P fertilizer (P-soil). During the 2.5-year, PV obtained sufficient P (1882 vs 2225 mg kg^–1) from PR-soils, with increased root biomass (33%) and root exudation (53%) compared to P-soils. In addition, its frond biomass increased by 20% consecutively with each harvest (six month interval) from 18 to 36 g plant^–1. Its frond biomass in PR-soils (52.2 g plant^–1 year^–1 or ∼12 mt ha^–1 year^–1) averaged 39% more than that in P-soils. To our knowledge, this represented the largest PV frond biomass reported, demonstrating the unique ability of PV in using insoluble P from PR in alkaline soils. In addition to biomass increase, PV from PR-soils had ∼1.5 times more As in fronds (2540, 780, and 920 mg kg^–1) than those from P-soils (1740, 570, and 400 mg kg^–1), with soils containing 129, 25, and 30 mg kg^–1 As, respectively. The low available P in PR-soils induced substantial plant growth and As uptake by PV. This translated into significantly more As removal from soil, averaging 48% reduction in PR-soils and 36% in P-soils in 2.5 years. With multiple harvests and PR amendments, our results showed As removal by PV from contaminated soils was ∼7 times faster than published studies