Next Article in Journal
Optimization Model of the Ecological Water Replenishment Scheme for Boluo Lake National Nature Reserve Based on Interval Two-Stage Stochastic Programming
Previous Article in Journal
Factors Driving Long Term Declines in Inland Fishery Yields in the Mekong Delta
Article

Hotspots of Legacy Phosphorus in Agricultural Landscapes: Revisiting Water-Extractable Phosphorus Pools in Soils

Department of Environmental Science and Technology, University of Maryland, College Park, MD 20547, USA
*
Author to whom correspondence should be addressed.
Academic Editor: Riccardo Scalenghe
Water 2021, 13(8), 1006; https://doi.org/10.3390/w13081006
Received: 16 March 2021 / Revised: 3 April 2021 / Accepted: 4 April 2021 / Published: 7 April 2021
(This article belongs to the Section Aquatic Systems—Quality and Contamination)
Controlling phosphorus (P) losses from intensive agricultural areas to water bodies is an ongoing challenge. A critical component of mitigating P losses lies in accurately predicting dissolved P loss from soils, which often includes estimating the amount of soluble P extracted with a laboratory-based extraction, i.e., water-extractable P (WEP). A standard extraction method to determine the WEP pool in soils is critical to accurately quantify and assess the risk of P loss from soils to receiving waters. We hypothesized that narrower soil-to-water ratios (1:10 or 1:20) used in current methods underestimate the pool of WEP in high or legacy P soils due to the equilibrium constraints that limit the further release of P from the solid-to-solution phase. To investigate P release and develop a more exhaustive and robust method for measuring WEP, soils from eight legacy P fields (Mehlich 3–P of 502 to 1127 mg kg−1; total P of 692 to 2235 mg kg−1) were used for WEP extractions by varying soil-to-water ratios from 1:10 to 1:100 (weight:volume) and in eight sequential extractions (equivalent to 1:800 soil-to-water ratio). Extracts were analyzed for total (WEPt) and inorganic (WEPi) pools, and organic (WEPo) pool was calculated. As the ratios widened, mean WEPi increased from 23.7 mg kg−1 (at 1:10) to 58.5 mg kg−1 (at 1:100). Further, WEPi became the dominant form, encompassing 92.9% of WEPt at 1:100 in comparison to 79.0% of WEPt at 1:10. Four of the eight selected soils were extracted using a 1:100 ratio in eight sequential extractions to fully exhaust WEP, which removed a cumulative WEPt of 125 to 549 mg kg−1, equivalent to 276–416% increase from the first 1:100 extraction. Although WEP concentrations significantly declined after the first sequential extraction, WEP was not exhausted during the subsequent extractions, indicating a sizeable pool of soluble P in legacy P soils. We conclude that (i) legacy P soils are long-term sources of soluble P in agricultural landscapes and (ii) the use of a 1:100 soil-to-water ratio can improve quantification and risk assessment of WEP loss in legacy P soils. View Full-Text
Keywords: water-extractable phosphorus; extraction ratios; phosphorus saturation; agriculture; legacy soils; water quality water-extractable phosphorus; extraction ratios; phosphorus saturation; agriculture; legacy soils; water quality
Show Figures

Graphical abstract

MDPI and ACS Style

Roswall, T.; Lucas, E.; Yang, Y.-Y.; Burgis, C.; Scott, I.S.P.C.; Toor, G.S. Hotspots of Legacy Phosphorus in Agricultural Landscapes: Revisiting Water-Extractable Phosphorus Pools in Soils. Water 2021, 13, 1006. https://doi.org/10.3390/w13081006

AMA Style

Roswall T, Lucas E, Yang Y-Y, Burgis C, Scott ISPC, Toor GS. Hotspots of Legacy Phosphorus in Agricultural Landscapes: Revisiting Water-Extractable Phosphorus Pools in Soils. Water. 2021; 13(8):1006. https://doi.org/10.3390/w13081006

Chicago/Turabian Style

Roswall, Taylor; Lucas, Emileigh; Yang, Yun-Ya; Burgis, Charles; Scott, Isis S.P.C.; Toor, Gurpal S. 2021. "Hotspots of Legacy Phosphorus in Agricultural Landscapes: Revisiting Water-Extractable Phosphorus Pools in Soils" Water 13, no. 8: 1006. https://doi.org/10.3390/w13081006

Find Other Styles
Note that from the first issue of 2016, MDPI journals use article numbers instead of page numbers. See further details here.

Article Access Map by Country/Region

1
Search more from Scilit
 
Search
Back to TopTop