『Abstract
Phosphorus (P) is an essential element in crop nutrition, which
can be growth limiting or an environmental contaminant, if present
in excess. Tillage practices have a direct effect on the behavior
and availability of soil P. Sorption and availability of various
P forms were evaluated in an incubation-fractionation study of
three soils, a Typic Paleudults (CR soil) and two Cerrado Oxisols
(Latossolo Vermelho-Amarelo [LVA] and Latossolo Vermelho [LV])
with distinct biogeochemical characteristics and tillage management
history. Phosphate and myo-inositol hexakisphosphate (mIPH) were
strongly sorbed by the soils. Maximum adsorption capacities (Smax) were 2.2-6.9, 3.3-7.8, and 1.6-19.8 mmol
kg-1 for phosphate in the 0-40 cm depths of the CR,
LV, and LVA soils, respectively. For mIPH, Smax
were 1.2-3.7, 3.7-5.5, and 4.6-5.2 mmol kg-1. Saturation
indices reflected the long-term effect of repeated manure applications
on the Paleudults and the near saturation of its P holding capacity,
in contrasts to the recently cultivated Cerrado soils. Tillage
method appeared to have altered P retention characteristics of
the near-surface zone very slightly, while increases in ligand-exchangeable
(EEPi) and enzyme-labile organic P (EDTA-PHP)
forms were observed in no-till Oxisols. In the Paleudults, added
manure P increased bioactive P fractions and P saturation of no-till
near-surface soil zone. Estimates of all bioactive P fractions
using the ligand-based enzymatic assay showed it to be an effective
method for assessing P availability in soil and developing sustainable
P management strategies, particularly in Cerrado Oxisols that
were low in organic matter while having an extensive P-fixing
capacity.
Keywords: Enzyme-hydrolyzable phosphorus; Phytate; Conventional
tillage; no-tillage; Phosphorus sorption-desorption』
1. Introduction
2. Material and methods
2.1. Soils
2.2. Phosphate and myo-inositol hexakisphosphate sorption and
desorption
2.3. Soil P fractionation
2.4. Statistical analysis and numerical methods
3. Results and discussion
3.1. Phosphorus sorption-desorption
3.2. Soil bioactive P fractions
3.2.1. EEPi
3.2.2. EDTA-PHP
4. Summary and conclusions
Acknowledgement
References
※生活性リンの分別は、Dao（2004,2007）による。