Citation:

Hettiarachchi, G. M., M. J. McLaughlin, K. G. SCHECKEL, D. J. Chittleborough, M. Newville, S. Sutton, AND E. Lombi. Evidence For Different Reaction Pathways For Liquid And Granular Micronutrients In A Calcareous Soil. SOIL SCIENCE SOCIETY OF AMERICA JOURNAL. Soil Science Society of America, Madison, WI, 72(1):98-110, (2008).

Impact/Purpose:

To investigate the distribution of fertilizer Mn and Zn in soil in situ and to understand whether the reaction products and primary Mn and Zn sinks around granular fertilizers and in fluid fertilizer bands were similar or not.

Description:

The benefits of Mn and Zn fluid fertilizers over conventional granular products in calcareous sandy loam soils have been agronomically demonstrated. We hypothesized that the differences in the effectiveness between granular and fluid Mn and Zn fertilizers is due to different Mn and Zn reaction processes in and around fertilizer granules and fluid fertilizer bands. We used a combination of several synchrotron-based x-ray techniques, namely, spatially resolved micro-x-ray fluorescence (µ-XRF), micro-x-ray absorption near edge structure spectroscopy (µ-XANES), and bulk-XANES and -extended x-ray absorption fine structure (EXAFS) spectroscopy, along with several laboratory-based x-ray techniques to speciate different fertilizer-derived Mn and Zn species in highly calcareous soils to understand the chemistry underlying the observed differential behavior of fluid and granular micronutrient forms. Micro-XRF mapping of soil-fertilizer reactions zones indicated that the mobility of Mn and Zn from liquid fertilizer was greater than that observed for equivalent granular sources of these micronutrients in soil. After application of these micronutrient fertilizers to soil, Mn and Zn from liquid fertilizers were found to remain in comparatively more soluble solid forms, such as hydrated Mn phosphate-like, Mn calcite-like, adsorbed Zn-like, and Zn silicate-like phases, whereas Mn and Zn from equivalent granular sources tended to transform into comparatively less soluble solid forms such as Mn oxide-like, Mn carbonate-like, and Zn phosphate-like phases.

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