『Abstract
Studies on phosphorus (P) reactions over time and the role of
organic matter in calcareous soils are important for developing
P fertilizers an manure management practices. This study was conducted
to determine the effects of time, soil properties and manure on
Olsen-P and its chemical forms in calcareous soils. Eight soil
samples were treated with two levels of inorganic P (0 and 300
mg kg-1) and two levels of manure (0 and 1%, w/w).
Olsen-P was determined at 2, 5, 10, 30, 60, 90 and 150 days of
incubation. Phosphorus fractionated to NaCl + NaOH-P, citrate
bicarbonate (CB-P), citrate bicarbonate dithionate (CBD-P), acetic
acid-sodium acetate (OAc) and HCl (HCl-P) after 5, 30 and 150
days. Olsen-P, in P-treated soils, showed a positive correlation
with the NH4OAc extractable Al and active
CaCO3. Increases in recovery as CBD-P revealed
that Fe oxides play an important role in P sorption during 0-30
days. The relative distribution of P fractions and Olsen-P followed
the order of HCl-P>OAc-P>Organic-P>CBD-P>Olsen-P>NaCl-NaOH-P.
The CB-P fraction was not measurable. Application of manure along
with P increased the recovery of applied P and recovery as CBD-P
compared with the P treatment. In general, manure application
had an appreciable and different impact on the chemical fractions
of P in calcareous soils as P from manure gradually turned into
available forms over the time.
Keywords: Phosphorus fractions; Calcareous soils; Manure; Olsen
P』
1. Introduction
2. Materials and methods
2.1. Experimental design
3. Results and discussion
4. Conclusions
References