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Mobility and Lability of Phosphorus from Granular and Fluid Monoammonium Phosphate Differs in a Calcareous Soil
Author(s) -
Lombi E.,
McLaughlin M. J.,
Johnston C.,
Armstrong R. D.,
Holloway R. E.
Publication year - 2004
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj2004.6820
Subject(s) - lability , calcareous , soil water , chemistry , phosphorus , fertilizer , phosphate , diffusion , environmental chemistry , soil science , environmental science , geology , paleontology , biochemistry , organic chemistry , physics , thermodynamics
Phosphorus availability is a major factor limiting crop production in highly calcareous soils. Recent field trials on calcareous soils in southern Australia have shown that fluid fertilizers may provide a useful alternative to granular fertilizer products. Fluid sources of P enhance P uptake and yield when compared with granular fertilizers applied at the same rate. This work aimed to compare the behavior of one fluid (technical grade monoammonium phosphate, TG‐MAP) and one granular (monoammonium phosphate, MAP) form of P fertilizer in a highly calcareous soil. Changes in soil pH, P diffusion, solubility, and lability (using isotopic dilution techniques) were determined at different distances from the point of application over 5 wk. Furthermore, reaction products in MAP granules were investigated using spectroscopic techniques. The results indicated that P from fluid TG‐MAP diffused more and was more available than P supplied as granular MAP. Also, X‐ray diffraction (XRD) and energy dispersive X‐ray microanalyses (EDXMA) of the MAP granules indicated that a significant percentage (12%) of the initial P remained in the granules even after 5 wk of incubation in the soil. The enhanced P availability of fluid fertilizers observed in field trials compared with granular forms is discussed in relation to differences in the dissolution, diffusion, and reaction processes in soils.