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Soil Science Society of America Journal Abstract - Soil Fertility & Plant Nutrition

Fluid Fertilizers Improve Phosphorus Diffusion but not Lability in Andisols and Oxisols

 

This article in SSSAJ

  1. Vol. 78 No. 1, p. 214-224
     
    Received: Feb 24, 2013
    Published: January 30, 2014


    * Corresponding author(s): daniela.montalvogrijalva@adelaide.edu.au
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doi:10.2136/sssaj2013.02.0075
  1. Daniela Montalvo *a,
  2. Fien Degryseb and
  3. Mike J. McLaughlinc
  1. a Soil Science School of Agriculture Food and Wine University of Adelaide PMB 1 Glen Osmond, SA 5064 Australia and CSIRO Land and Water PMB 2 Glen Osmond, SA 5064 Australia
    b Soil Science School of Agriculture Food and Wine University of Adelaide PMB 1 Glen Osmond, SA 5064 Australia
    c Soil Science School of Agriculture Food and Wine University of Adelaide PMB 1 Glen Osmond, SA 5064 Australia and CSIRO Land and Water PMB 2 Glen Osmond, SA 5064 Australia

Abstract

Fluid phosphorus (P) fertilizers increase availability of P in calcareous soils compared with granular fertilizers, because of reduced P precipitation. It is unclear whether fluid P forms may also enhance fertilizer P availability in acidic soils. A 35-d incubation experiment assessed the diffusion, lability, and solubility of P from granular (calcium phosphate and ammonium phosphate) and fluid (ammonium phosphate and polyphosphate) fertilizers in two Andisols and two Oxisols. A calcareous Inceptisol and an Alfisol were included for comparison. Phosphorus diffusion and lability was assessed using a novel visualization technique and isotopic exchange (24-h equilibration), and residual fertilizer granules were analyzed at the end of the incubation. Most P (90%) diffused out of the granules, except for calcium phosphate fertilizers in the calcareous soil. In the strongly P-sorbing soils (acidic and calcareous), P applied in fluid form diffused further from the application point compared with granular P. However, in the Andisols and Oxisols, the greater diffusion did not result in greater P lability and solubility; more P remained labile with the granular (34% on average) than with the fluid fertilizer (24%). In contrast, in the calcareous soil, the application of fluid P resulted in enhanced P lability and solubility. These results suggest that in Andisols and Oxisols, where strong adsorption rather than precipitation reactions limit fertilizer P availability, spreading the fertilizer over a larger soil volume by using fluid formulations may reduce P lability. No agronomic benefit over granular products is expected from the use of fluid P fertilizers in these soil types.

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