『Abstract
The Hedley sequential-phosphorus (P)-fractionation method has
been used in many countries to study the effects of land-use and
management systems on soil P. Many data sets have been obtained
but collectively never have been considered or to goal topic reviewed.
Therefore, the objectives of this review were to compile and systematically
evaluate these data. The data generated over many years were grouped
into temperate, and subtropical and tropical soils of different
land use and duration of soil-management studies. In natural ecosystems,
vegetation types and composition and percent of vegetation covers
substantially affected all P fractions with pronounced impacts
on the labile and moderately labile P. In short-term studies (≦10
y), changes in the labile and moderately labile inorganic P (Pi) fractions were detected when more P (e.g.,
by factor 5) was applied than commonly recommended for agricultural
crops. However, without P application the changes in all P fractions
were subtle in temperate soils, but declines were significant
in labile and moderately labile P in subtropical and tropical
soils. In both temperate and tropical climates, medium (10-25
y) and long-term (>25 y) cultivation without P application depleted
all P fractions, whereas most of P fractions increased with continuous
P application, regardless of the amount and source of P. Synthesis
of data resulted in multiple-regression functions which described
differences in labile and moderately labile P fractions as function
of differences in amount of P application and duration of the
experiments. Moreover, the correlation analysis also showed strong
association among most of the P fractions. Current limitations
in data interpretation of Hedley fractionation can be overcome
by the application of 31P nuclear magnetic resonance
(NMR) and X-ray absorption near-edge fine-structure (XANES) spectroscopy.
Key words: soil phosphorus; P speciation; labile P; moderately
labile P; stable P; temperate soils; tropical soils; 31P
NMR; P XANES』
1. Introduction
2. Methods of data mining and evaluation
3. Effects of land use and management on P fractions in temperate
soils
3.1. Native vegetation covers
3.2. Effects of short-term land-use and management systems
3.2.1. Incubation studies
3.2.2. Short-term field studies
3.2.3. Phosphorus losses
3.3. Effects of medium-term land-use and management systems
3.4. Effects of long-term land-use and management systems
4. Effects of land use and management on P fractions in subtropical
and tropical soils
4.1. Native vegetation covers and toposequence
4.2. Effects of short-term land use and management systems
4.2.1. Incubation studies
4.2.2. Pot experiments
4.2.3. Short-term field studies
4.3. Effects of medium- and long-term land-use and management
systems
5. Synthesis: Effect of P application and time on labile and moderately
labile P fractions
6. Phosphorus speciation by 31P NMR and X-ray absorption
near-edge structure spectroscopy
7. Conclusions
Acknowledgments
References