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Formulation, synthesis and characterization of boron phosphate (BPO 4 ) compounds as raw materials to develop slow‐release boron fertilizers
Author(s) -
Abat Margaret,
Degryse Fien,
Baird Roslyn,
McLaughlin Michael J.
Publication year - 2014
Publication title -
journal of plant nutrition and soil science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.644
H-Index - 87
eISSN - 1522-2624
pISSN - 1436-8730
DOI - 10.1002/jpln.201400234
Subject(s) - solubility , boron , boric acid , dissolution , chemistry , phosphate , phosphoric acid , nuclear chemistry , leaching (pedology) , crystallinity , ammonium , inorganic chemistry , organic chemistry , soil water , environmental science , soil science , crystallography
We investigated the use of boron phosphate (BPO 4 ) as a slow‐release boron (B) source. Boron phosphate compounds were synthesized by mixing boric acid (H 3 BO 3 ) and phosphoric acid (H 3 PO 4 ) and heating at temperatures of 25 to 1000°C for 1 or 24 h. X‐ray diffraction (XRD) patterns and chemical analysis confirmed the formation of BPO 4 . The crystallinity of these compounds increased with increasing temperature and heating time. The compounds synthesized at 300°C or less were hygroscopic and clumped together, while those synthesized at 500 to 1000°C were non‐hygroscopic and free‐flowing. The solubility of these compounds was assessed at different pH and P concentrations, and compared to the solubility of ulexite and colemanite. The solubility of the BPO 4 compounds decreased with increasing synthesis temperature and with decreasing pH. The solubility and the kinetics of B release from BPO 4 compounds synthesized at 500 and 800°C were slower than for most commonly used B sources. Given their slow dissolution, the BPO 4 compounds may have potential to continuously supply B to crops in environments where B leaching is a problem. The compounds synthesized at 500 and 800°C show potential for co‐granulation with macronutrient fertilizers such as mono‐ammonium phosphate to produce slow‐release B‐enriched granules.