Controlled drainage is considered as a soil management tool to improve water supply to crops and reduce nutrient losses from fields; however, its closure may affect phosphorus (P) mobilization in soil. To assess the P mobilization potential, three soil profiles with redoximorphic features were selected along a slight hill in Northern Germany. Soil samples from three depths of each profile were characterized for basic properties, total element content, oxalate- and dithionite-extractable pedogenic Al, Fe and Mn (hydr)oxides, P pools (sequential extraction), P species [P K-edge X-ray absorption near-edge structure (XANES) spectroscopy] and P sorption behavior. In topsoil (similar to 10 cm depth), labile P (H2O-P + resin-P + NaHCO3-P) accounted for 26-32% of total P (P-t). Phosphorus K-edge XANES revealed that up to 49% of P-t was bound to Al and/or Fe (hydr)oxides, but sequential fractionation indicated that > 30% of this P was occluded within sesquioxide aggregates. A low binding capacity for P was demonstrated by P sorption capacity and low K-f coefficients (20-33 mg1-nfLnfkg-1) of the Freundlich equation. In the subsoil layers (similar to 30 and similar to 65 cm depth), higher proportions of Al- and Fe-bound P along with other characteristics suggested that all profiles might be prone to P mobilization/leaching risk under reducing conditions even if the degree of P saturation (DPS) of a profile under oxic conditions was < 25%. The results suggest that a closure of the controlled drainage may pose a risk of increased P mobilization, but this needs to be compared with the risk of uncontrolled drainage and P losses to avoid P leaching into the aquatic ecosystem.
| ENVIRONMENTAL GEOCHEMISTRY AND HEALTH DOI: 10.1007/s10653-020-00561-y Early access iconEarly Access: APR 2020 |
| Baumann, Karen; Shaheen, Sabry M.; Hu, Yongfeng; Gros, Peter; Heilmann, Elena; Morshedizad, Mohsen; Wang, Jianxu; Wang, Shan-Li; Rinklebe, Jorg; Leinweber, Peter |
Univ Rostock, Fac Agr & Environm Sci, Soil Sci, Justus von Liebig Weg 6, D-18051 Rostock, Germany.
|Author(s) from IGCAS || WANG Jianxu |
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