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Soil Science Society of America Journal Abstract - Soil Chemistry

Speciation and Distribution of Phosphorus in a Fertilized Soil


This article in SSSAJ

  1. Vol. 70 No. 6, p. 2038-2048
    Received: Feb 5, 2006

    * Corresponding author(s): enzo.lombi@csiro.au
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  1. E. Lombi *a,
  2. K. G. Scheckelb,
  3. R. D. Armstrongc,
  4. S. Forrestera,
  5. J. N. Cutlerd and
  6. D. Patersone
  1. a CSIRO Land and Water, PMB 2 Glen Osmond, SA 5064, Australia
    b USEPA, National Risk Management Research Lab., 5995 Center Hill Ave., Cincinnati, OH 45224
    c Department of Primary Industries, Natimuk Rd., PB 260, Horsham, VIC 3400, Australia
    d Canadian Light Source Inc., Saskatoon, SK S7N 0X4, Canada
    e Advanced Photon Source, Argonne National Lab., Bldg. 431 B008, Argonne, IL 60439-4856


Phosphorus availability is often a limiting factor for crop production around the world. The efficiency of P fertilizers in calcareous soils is limited by reactions that decrease P availability; however, fluid fertilizers have recently been shown, in highly calcareous soils of southern Australia, to be more efficient for crop (wheat [Triticum aestivum L.]) P nutrition than granular products. To elucidate the mechanisms responsible for this differential response, an isotopic dilution technique (E value) coupled with a synchrotron-based spectroscopic investigation were used to assess the reaction products of a granular (monoammonium phosphate, MAP) and a fluid P (technical-grade monoammonium phosphate, TG-MAP) fertilizer in a highly calcareous soil. The isotopic exchangeability of P from the fluid fertilizer, measured with the E-value technique, was higher than that of the granular product. The spatially resolved spectroscopic investigation, performed using nano x-ray fluorescence and nano x-ray absorption near-edge structure (n-XANES), showed that P is heterogeneously distributed in soil and that, at least in this highly calcareous soil, it is invariably associated with Ca rather than Fe at the nanoscale. “Bulk” XANES spectroscopy revealed that, in the soil surrounding fertilizer granules, P precipitation in the form of octacalcium phosphate and apatite-like compounds is the dominant mechanism responsible for decreases in P exchangeability. This process was less prominent when the fluid P fertilizer was applied to the soil.

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