Pedosphere 34(3): 631--640, 2024
ISSN 1002-0160/CN 32-1315/P
©2024 Soil Science Society of China
Published by Elsevier B.V. and Science Press
| Increasing phosphorus fertilizer value of recycled iron phosphates by prolonged flooding and organic matter addition |
Rochelle Joie SARACANLAO1 , Hannah VAN RYCKEL1, Mieke VERBEECK2, Maarten EVERAERT1, Erik SMOLDERS1 |
1 Division of Soil and Water Management, Department of Earth and Environmental Science, KU Leuven, Kasteelpark Arenberg 20, Heverlee B-3001 (Belgium);
2 Soil Service of Belgium. Willem De Croylaan 48, Leuven 3001 (Belgium) |
| Corresponding Author:Rochelle Joie SARACANLAO |
| ABSTRACT |
| Iron (Fe) minerals are commonly used to remove phosphorus (P) from waste streams, producing P-loaded Fe(III) oxides or Fe(II) phosphate minerals (e.g., vivianite). These minerals may be used as fertilizers to enhance P circularity if solubilized in soil. Here, we tested the P fertilizer value of recycled Fe phosphates (FePs) in a pot trial and in an incubation experiment, hypothesizing that P release from FePs is possible under Fe(III)-reducing conditions. First, a pot trial was set up with rice (Oryza sativa) in all combinations of soil flooding or not, three P-deficient soils (acid, neutral, and calcareous), and six FePs (three Fe(III)Ps and three Fe(II)Ps) referenced to triple superphosphate (TSP) or zero amendments. Shoot P uptake responded to TSP application in all treatments but only marginally to FePs. The redox potential did not decrease to -200 mV by flooding for a brief period (13 d) during the pot trial. A longer incubation experiment (60 d) was performed, including a treatment of glutamate addition to stimulate reductive conditions, and P availability was assessed with CaCl2 extraction of soils. Glutamate addition and/or longer incubation lowered soil redox potential to < -100 mV. On the longer term, Fe(III) minerals released P, and adequate P was reached in the calcareous soil and in the neutral soil amended with Fe(III)P-sludge. It can be concluded that prolonged soil flooding and organic matter addition can enhance the P fertilizer efficiency of FePs. Additionally, application of FeP in powder form may enhance P availability. |
| Key Words: agronomic efficiency,circular economy,P-loaded Fe(III) oxides,paddy soil,vivianite,redox |
| Citation: Saracanlao R J, Van Ryckel H, Verbeeck M, Everaert M, Smolders E. 2024. Increasing phosphorus fertilizer value of recycled iron phosphates by prolonged flooding and organic matter addition. Pedosphere. 34(3): 631–640. |
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