Phosphate Adsorption by various Soils of Kenya

Abstract

The inllucnce of soil physico-chemical properties on P adsorption in six Kenyan soils collected from various parts country of the was evaluated' Soil samples lvere collected from the 0-l5cm and l5-30 cm depths o unfertilized plots. The samples represented ranges in: pH (4'5 - 7'5), organic C (s.2 - 9s.6 g kg-r), CEC (15,2 - 40.6 cmol (+) kg,), oxaiate extractable Fe (50'l-340.2mmolkg-'),andoxalateextractableAl(74,1 -llt2mmol kg''), Batchincubationswercusedtomcasurethep adsorption capacity ofthe soir sa,rpres. Sorption maxima firr the soirs ianged from 29.7 mmor p kg-r for the inceptisor to 217'5 mmol P kg-'for thc andisol sample. The sorption maxima werc highly correlated (p<0.001) with HCI and oxalate- extractable Fe and Al, citrate-dithionite-bicarbonate (CDB)-Al and NaoA-extractable p. Thesc correlations reyeal that p sorption in the soils studied is dominated bv the amorphous lbrms of Fe and Al and measurcs ofthese pools can be rrsed asindicators of P fertilizer efliciency in these soils.