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Relationship between Olsen P and ammonium lactate–extractable P in portuguese acid soils
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Advisor(s)
Abstract(s)
The soil phosphorus (P) test in Portugal is based on extraction with ammonium lactate
(AL) at acidic pH. Because this test is rarely used in other countries, it is desirable to
see whether the AL-P values correlate with the more commonly used P tests. In this
work, we compared AL-P with bicarbonate-extractable P (Olsen’s method) for a group
of 48 samples from Portuguese acidic soils differing widely in P status. Despite their
contrasting composition, both reagents extracted phosphate from the same sources,
albeit in different proportions. Both Olsen P and AL-P were strongly correlated with
resin-extractable and dilute electrolyte-desorbable P, which are respectively related to
the soil contents in phytoavailable P and P that can be released to runoff or drainage
water. Olsen P and AL-P were strongly correlated (R2 = 0.870), the correlation became
stronger when three overfertilized soils were excluded (Olsen P = 2.35 + 0.45 AL-P;
R2 = 0.908; P ≤ 0.001, n = 45). No correlation was observed for a group of soils
recently fertilized with Gafsa phosphate probably because the acidic AL reagent dissolved
residual calcium phosphate, thus overestimating the soil content in desorbable P.
On the basis of the present results and the AL-P-based fertility classes used for fertilizer
recommendation purposes, Olsen P–based fertility classes were tentatively proposed
for Portuguese acidic soils.
Description
DOI: 10.1080/00103624.2010.508296
Keywords
Ammonium lactate method Olsen method Soil phosphorus
Citation
MONTEIRO, M.C.H. [et al.] (2010) - Relationship between Olsen P and ammonium lactate–extractable P in portuguese acid soils. In Communications in Soil Science and Plant Analysis. ISSN 0010-3624. 41. P. 2358-2370