Phosphate retention in some tropical soils in relation to soil taxonomic classes

Phosphate sorption values were correlated with other properties, the most ‐important factor relared to P retention seem to be extractable aluminium, free iron oxides also play a significant role in the process of sorption. Clay content affects P‐sorption but only at low level of significance. When adsorption was studied in relation to soil classes, it was found that there is a great variability in oxisols, and within them the oxisol with har‐dened laterite presented the lowest sorbing power. All the ultisols studied had low P‐retention. The ver‐tisols presented moderate to high P‐retention charac‐teristics. In general the entisols present the lowest P‐sorption in tropical soils. Only two alfisols (with a low capacity to sorb phosphate) were included making any comparison difficult. The only inceptisol examined showed high P‐sorption capacity