Fjölrit RALA - 15.06.2004, Blaðsíða 125

P ads max mgkg'1
Figure 2 Linear relationship between Al0 % + 1/2 Fe0 % and the P adsorption maxima of
European volcanic soils
Conclusions:
• The Langmuir isotherms describes well the phosphate adsorption phenomena in a
large interval (0 and more then 10 000 mg kg ').
• Allophane content (Alo+1/2 Feo %) explains in 72 percent the phosphate sorption
capacity of soils (Fig.2). In some cases the bases could be the possible further
explanation for some part of the remaining 28 percent. There is a hyperbolic
relationship between the bases and P adsorption maxima. The very low bases correlate
well with high P adsorption maxima (No5; No6 and NolO).
• Oxalate soluble A1 alone explains the P adsorption the same rate as allophane, Fe0
alone somewhat less.
• In some cases Al0+l/2Fe0 over estimate the P adsorption maximum (No6 B and Nol5
A and B horizons) and in some cases underestimate it (No5, NolO).
• In the case of NolO Bw3b horizon the extremely high dithionite soluble Fe
responsible for the discrepancy.
• Adding pirophosphate soluble A1 to the Al0 values the increase of R2 is very small.
References
Fiileky Gy., and Tolner L. Gemeinsames Modell der P-Adsorption und P-Desorption in
Boden. Tagungsbericht Nr.289 Justus von Liebigs Werk - Wegbereiter der
wissensachaftlich begriindeten Diingung, Adl Berlin, pp 291-298 (1990)
Mizota C., and L. P. van Reewirjk. Clay mineralogy and chemistry of soils formed in volcanic
material in diverse climatic regions. ISRIC, Wageningen 1989
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