Isotopic dilution, Microscopic and Spectroscopic Techniques for Understanding Different Reaction Pathways for Liquid- and Granular-Micronutrients in Calcareous Soils.
Ganga Hettiarachchi, CSIRO Land & Water/University of Adelaide, PMB 2, Glen Osmand, SA 5064, Australia, Michael McLaughlin, CSIRO Land and Water, CSIRO Land and Water, PMB 2, Glen Osmond, SA 5064, AUSTRALIA, Kirk Scheckel, US-EPA(Environ. Protection Agency), US EPA, 5995 Center Hill Avenue, Cincinnati, OH 45224-1702, David Chittleborough, PMB1, University of Adelaide, University Of Adelaide, Dept. Of Soil Science, Glen Osmond, 5005, AUSTRALIA, and Matthew Newville, Consortium for Advanced Radiation Sources, The University of Chicago, 9700 South Cass Avenue, Bldg. 434A, Argonne, IL 60439.
Differential behaviour (plant response in terms of yield and/or concentration in grain) of fluid and granular micronutrient forms have been repeatedly observed in field trials conducted in highly calcareous soils. We employed isotopic dilution techniques, electron microscopy, x-ray diffraction (XRD) and several synchrotron based x-ray techniques namely, micro-x-ray fluorescence; micro-x-ray absorption near edge structure spectroscopy (micro-XANES); micro XRD and “bulk” XANES/extended x-ray absorption fine structure spectroscopy, to study the behavior and reaction products of different fertilizer derived-Cu, -Mn, and -Zn in highly calcareous soils. Combined use of different techniques suggested that, when fluid micronutrients were applied to soil, not only did these micronutrients diffuse further away from the point of application, but they also remained in comparatively more soluble solid forms. In contrast, granular micronutrients diffused comparatively little (Mn) or remained within the granule (Cu, Zn), and tended to transform into comparatively less soluble solid forms. Combined use of synchrotron techniques with more conventional x-ray and isotopic techniques are useful for the examination of complex soil:fertilizer reaction zones and aid our understanding of the reaction products of micronutrients applied to soil.