『Summary
Phosphorus (P) speciation in 21 basaltic and four non-basaltic
Irish grassland soils was determined by NaOH-EDTA extraction and
31P NMR spectroscopy. Organic P in basaltic soils ranged
between 30 and 697 mg P kg-1 and consisted of phosphate
monoesters (84-100%), DNA (0-16%) and phosphonates (0-5%). Inorganic
P was mainly phosphate (83-100%) with small concentrations of
pyrophosphate (0-17%). Phosphate monoesters were more important
as a proportion of extracted P in basaltic soils, probably because
of their greater oxalate-extractable Fe and Al contents. Phosphate
monoesters appeared to be strongly associated with non-crystalline
Al and increased with total soil P concentration, indicating that
they do accumulate in grassland soils. In non-basaltic soils myo-inositol
hexakisphosphate constituted between 20 and 52% of organic P,
while scyllo-inositol hexakisphosphate constituted between 12
and 17%. These compounds were not quantified separately in basaltic
soils because of poor NMR resolution in the phosphate monoester
region, but appeared to represent a considerable proportion of
the organic P in most samples. DNA concentrations were greater
in basaltic soils compared with non-basaltic soils and were associated
with acidic pH and large total C contents. The inability of the
Olsen P test to assess effectively the P status of basaltic soils
may result from strong phosphate sorption to Fe and Al oxides,
inducing plant utilization of soil organic P. Phosphorus nutrient
management should account for this to avoid over-application of
P and associated financial and environmental costs.』
Introduction
Materials and methods
Soil sampling and analysis
Solution 31P NMR spectroscopy
Results
Soil properties
Soil phosphorus
Correlations between soil properties and soil phosphorus
Discussion
Phosphorus speciation and soil properties
Implications for P plant availability
Conclusions
Acknowledgements
References