ZINC STUDIES IN ZIMBABWEAN SOILS - EFFECT OF PH AND PHOSPHORUS ON ZINC ADSORPTION BY 2 ZIMBABWEAN SOILS

Laboratory experiments were carried out to assess the effect of applic ation of different levels of lime, phosphorus, and zinc on zinc availa bility in two Zimbabwean soils. Laboratory incubation studies showed a very significant decrease in zinc availability with lime application. A pH increase of one unit was found to increase zinc sorption by abou t 100% in a sandy soil (Chiota) and 34% in a sandy clay loam soil (Gwe bi). Application of phosphorus was shown to result in decreased zinc a vailability. It was concluded that application of phosphorus affected zinc sorption by an indirect pH effect and also possibly by an indirec t CEC effect.