Phosphorus dynamics in long-term flooded, drained and reflooded soils

Authors: TIAN, JUAN - Jiangsu Normal University; DONG, GUIMING - China University Of Mining And Technology; KARTHIKEYAN, RAGHUPATHY - Texas A&M University; Harmel, Daren

Submitted to: Water, Air, and Soil Pollution
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/11/2017
Publication Date: 9/27/2017
Citation: Tian, J., Dong, G., Karthikeyan, R., Harmel, R.D. 2017. Phosphorus dynamics in long-term flooded, drained and reflooded soils. Water, Air, and Soil Pollution. Water 2017, 9(7), 531. doi:10.3390/w9070531.
DOI: https://doi.org/10.3390/w9070531

Interpretive Summary: In flooded areas, soils are often exposed to standing water and subsequent drainage, thus over fertilization can release excess phosphorus (P) into surface water and groundwater. To investigate P release and transformation processes in flooded soils, we flooded-drained-reflooded two soils for 35 days, then drained the soils, and 10 days later reflooded the soils for 17 days. Phosphorus (P) in standing floodwater, soil water, and in the soil analyzed. The wheat-growing soil had significantly higher floodwater P concentrations than did vegetable-growing soil, and floodwater P in both soils decreased with the number of flooding days. During the reflooding period, P in overlying floodwater from both soils was less than 0.87 mg/L, which was significantly lower than that during the flooding period. The concentration of P in soil water was greater than 1.26 mg/L after 12 days of flooding and greater than 0.7 mg/L after 4 days of reflooding. Our results suggest that changes in P levels in floodwater, soil water, and in the soil are significantly affected by fertilizing and flooding; therefore, careful fertilizer management should be employed on flooded soils to avoid excess P loss.

Technical Abstract: In flooded areas, soils are often exposed to standing water and subsequent drainage, thus over fertilization can release excess phosphorus (P) into surface water and groundwater. To investigate P release and transformation processes in flooded alkaline soils, we flooded-drained-reflooded two soils for 35 d, then drained the soils, and 10 d later reflooded the soils for 17 d. Dissolved reactive phosphorus (DRP), pH, and Eh in floodwater and pore water were analyzed. Soil inorganic P fractions and Olsen P were also investigated. The wheat-growing soil had significantly higher floodwater DRP concentrations than did vegetable-growing soil, and floodwater DRP in both soils decreased with the number of flooding days. During the reflooding period, DRP in overlying floodwater from both soils was less than 0.87 mg/L, which was significantly lower than that during the flooding period. The concentration of pore water DRP observed at a 5-cm depth was greater than 1.26 mg/L after 12 d of flooding and greater than 0.7 mg/L after 4 d of reflooding. Pore water DRP at 5 cm decreased over time, and pore water DRP concentrations decreased at deeper depths. P diffusion occurred from the top to the bottom of the soils. After flooding, Al-P increased in both soils, while Fe-P, O-P and Ca2-P decreased. After reflooding, Fe-P, Al-P, and O-P increased. When Olsen P in the vegetable-growing soil exceeded 180.7 mg/kg and Olsen P in the wheat-growing soil exceeded 40.8 mg/kg, the concentration of DRP in pore water increased significantly. Our results suggest that changes in floodwater and pore water DRP concentrations, soil inorganic P fractions, and Olsen P due are significantly affected by fertilizing and flooding; therefore, careful fertilizer management should be employed on flooded soils to avoid excess P loss.