posted on 2023-05-12, 08:44authored byMaarten 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.