Potassium (K) is not widely used as a commercial fertilizer for agricultural crop production such as barley in the Ethiopian condition, particularly in the study area. Thus, this study was initiated to identify the effective sources and evaluate rates of K application on yield and yield components of barley and to evaluate the effects of K on soil and plant tissue contents. A Field experiment was carried out during the 2014 main cropping season at Enda-mokoni district of the Tigray regional state, Ethiopia on Vertisols and Luvisols. The experiments were arranged in a randomized complete block design with three replications. There were thirteen treatments including the control, recommended N and P (46 kg N and 69 kg P2O5 ha-1), recommended N and P plus S (at a rate of 30 kg ha-1) and ten levels of K applied in the form of KCl and K2SO4 from each source (15, 30, 45, 60 and 75 kg K ha-1) with a full dose of basal application of recommended NP fertilizers for all treatments except the control. Composite surface soil samples before experimental trial and from each treatment after harvest were collected for laboratory analysis of selected soil properties. At harvest the result from the soil sample analysis, revealed that both soils are low in K content. Plant tissue and grain analysis revealed that low K contents of barley crop were obtained. The highest barley grain yield (3816.2 kg ha-1) and straw yield (8686.9 kg ha-1) were obtained from Luvisols. It was also observed that grain yield at the 60 kg K ha-1 in the form of KCl was biologically and economically sound whereas applied K in the form of K2SO4 was significant only in biological yield. In compliment to this the partial budget analysis was also revealed that application of 60 kg K ha-1 in the form of KCl gave a better economic advantage for both soil types. Hence, it could be concluded that use of KCl at a rate of 60 kg K ha-1 along with the recommended N and P could increase barley production and productivity in Vertisols and Luvisols.