Millions of hectares of arable land worldwide, particularly in arid and semi-arid regions, are deficient in plant available Zn and Mn. Thus, various organic and inorganic Zn/Mn fertilizers have been used to correct their deficiencies. Recent field studies conducted by our group have shown an increase response to fluid Zn (Zn concentration in grain) compared to granular fertilisers in calcareous sandy loam soils. We also showed increasing Zn response with increasing rates of fluid P/Zn while there was no Zn response with increasing granular P/Zn. This study aimed to improve our understanding of the chemical and physical processes underlying the differential efficiency of added Zn and Mn from various different sources (Zn incorporated monoammonium phosphate (Zn-MAP); Mn incorporated TSP, technical grade MAP+Zn+Mn; ammonium polyphosphate (APP)+Zn+Mn; suspension P+Zn+Mn; APP alone) in two diffrent soils. Results examining the diffusion of Zn and Mn from the point of fertilizer placement as well as their reaction products will be presented. The lability of Zn and Mn at different distances from the point of fertilizer placement measured using isotopic dilution techniques will also be discussed.