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Layered Transition Metal Molybdates as New Slow-Release Micronutrient Fertilizer Matrices for Zn, Cu, and Mo

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posted on 2023-05-12, 08:44 authored by Maarten Everaert, Ivan B. Andelkovic, Erik Smolders, Fien Degryse, Roslyn Baird, Michael J. McLaughlin
Micronutrient availability in agricultural soils is an important driver for crop production, and for mobile micronutrients, slow-release fertilizers can more efficiently enhance crop nutrition. In this study, for the first time, layered transition metal molybdates (LTMs) are proposed as slow-release fertilizer compounds for the micronutrients molybdenum (Mo), zinc (Zn), and copper (Cu). A series of LTMs were successfully prepared in varying synthesis conditions, characterized (inductively coupled plasma optical emission spectrometry, X-ray diffraction, Fourier transform infrared, and scanning electron microscopy), and tested for solubility in water. For three selected LTMs (Zn–Mo, Cu–Mo, and Zn–Cu–Mo), the solubility as a function of solution pH was determined. The LTMs showed limited stability in acidic conditions. Therefore, co-compaction of LTMs with pH neutral or alkaline macronutrient carriers [muriate of potash (MOP), limestone, rock phosphate] was explored. A Zn-based LTM co-compacted in a MOP carrier showed a useful slow and almost constant release rate of both Mo and Zn in a column dissolution test (Mo release reaching 32% after 72 h), while a reference compacted MOP fertilizer with soluble Mo released 90% of Mo after 4 h. Hence, a Zn-LTM could prove useful as a slow-release fertilizer or raw material to incorporate into non-acidic macronutrient fertilizers.

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