Sorghum production is constrained by terminal drought stress in semi-arid areas of north-eastern Ethiopia. Data from field experiments conducted in the region for two consecutive years (2015 - 2016) were used to investigate the effect of potassium (K) and NPSBZn-blended fertilizer (BF) inputs on the drought response of sorghum through analysis of gas exchange, dry matter accumulation and growth parameters. Leaf gas exchange properties varied strongly with K and BF application both under normal rainfall and drought conditions. Data taken at anthesis in drought-exposed sorghum indicated reduction of net photosynthetic rate (A(N)) with BF supply. A(N) declined from 15.7 mu mol CO2/m(2)/s in the control to 13.4 mu mol CO2/m(2)/s with application of 164 kg/ha BF. However, higher total dry matter yield was recorded at maturity in response to blended fertilizer and K inputs. Increasing supply of NPSBZn-blended fertilizer was associated with declining leaf K content, increasing intercellular CO2 concentration and water use efficiency (WUE) during anthesis. Significant variations in crop growth rates were also observed in response to K and BF inputs. At physiological maturity, net assimilation rate (NAR) increased with K and BF inputs both under drought and normal rainfall conditions. In general, K application modulated the response of sorghum to BF input under both normal rainfall and drought conditions. Therefore, grain sorghum could benefit from early supply of K and BF fertilizer in drought prone areas of Northeastern Ethiopia.