Effects of fertilisation on phosphorus pools in the volcanic soil of a managed tropical forest
Meason, D. F., T.W. Idol, J.B. Friday and P.G. Scowcroft . 2009. Forest Ecology and Management 258: 2199- 2206
Abstract
Acacia koa forests benefit from phosphorus fertilisation, but it is unknown if fertilisation is a short or long
term effect on P availability. Past research suggests that P cycling in soils with high P sorption capacity,
such as Andisols, was through organic pathways. We studied leaf P and soil P fractions in a tropical forest
Andisol for 3 years after fertilisation with triple super phosphate. Leaf P concentration and labile P
remained high after fertilisation. Fertilisation had increased all the inorganic P fractions over the length
of the study, while organic P fractions had not. The results suggested that the organic P fractions had a
reduced role as a source of labile P after fertilisation. The size and dynamics of the sodium hydroxide- and
hydrochloric acid-extractable P pools would suggest that either pool could be major sources of labile P.
Because of the high level of poorly crystalline minerals in Andisols (allophone and imogolite), it would be
expected that applied P would quickly lead to strong P sorption onto mineral surfaces and thus a rapid
decline in P availability. We propose that the high organic matter present in these soils had masked some
of the Al and Fe sorption sites, which allowed the sorption and desorption when large amounts of
addition P were applied.
Key Words
Hedley fractionation, Phosphorus fertilization, Andisol, Tropical forest, Acacia koa
