Evaluation of Six Phosphorus Extraction Methods for Compliance Testing of Recycled P Fertilizers
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Authors
Organisational units
External Organisational units
- BOKU
- Research Institute of Organic Agriculture FiBL
- Natural Resources Institute Finland, Jokioianen
- University of South Australia
- Bodengesundheitsdienst GmbH, Ochsenfurt, Germany
- Departamento de Agronomía, ETSIA, Universidad de Sevilla, Ctra Utrera km 1, 41013, Sevilla, Spain
- Canadian Light Source, University of Saskatchewan, 44 Innovation Place, Saskatoon, SK Canada
- AGRANA Research & Innovation Center (ARIC). Reitherstrasse 21-23, 3430 Tulln an der Donau, Austria
- Justus-Liebig-Universität Gießen
- AGRANA Research & Innovation Center GmbH
Abstract
Phosphorus (P) recycling for fertilizer production addresses the dependency on phosphate rock and mitigates P losses to the environment. However, predicting plant-available P in recycled fertilizers is challenging due to their diverse chemical composition. This study aimed at identifying the most suitable P extraction method for fertilizer compliance testing, considering their correlation with actual fertilization efficiency, as well as their simplicity, throughput, recognition and cost. Studies on fertilizer P compliance testing often lack recommendations on minimum P extractability threshold values. Here, thresholds are calculated based on actual fertilization efficiency of a large, chemically diverse set of recycled P fertilizers, many of which are already marketed. Thirty recycled P fertilizers were extracted with H2O, neutral ammonium citrate (NAC), electro-ultrafiltration (EUF), ferrihydrite-filled membranes (iron bag; IB), sodium bicarbonate (NaHCO3) and diffusive gradients in thin films (DGT). The mineral replacement value (MRV) of the fertilizer set was previously evaluated in three pot experiments at a fertilization rate of 50 mg kg−1 soil. MRV correlations with the extractions methods showed similar results for all besides H2O, which cannot be a reliable indicator for P availability. Fertilizers were classified as efficient or inefficient based on their MRV exceeding or falling below 60 % of the triple superphosphate reference value. The minimum P extractability threshold value (MPETV) for each method was based on the efficiency classification and it minimized the number of misclassified fertilizers. NAC, with a 60 % extractable minimum P threshold value, was the most adequate method for compliance testing, despite its overestimation of iron phosphate availability.
Details
Original language | English |
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Article number | 103913 |
Number of pages | 15 |
Journal | Environmental technology & innovation (OA) |
Volume | 37.2025 |
Issue number | February |
DOIs | |
Publication status | Published - 27 Nov 2024 |