Crop responses to potassium in Pakistan are sporadic. Furthermore farmers are reluctant to use K fertilizer, depleting K in soil. Cultivation of efficient K-utilization genotypes may be a promising alternate strategy. Therefore, an experiment was conducted in the greenhouse of the Institute of Soil and Environmental Sciences, University of Agriculture, Faisalabad to study the differential growth response and K-utilization efficiency among cotton genotypes. We evaluated growth response and potassium utilization efficiency of 7 cotton cultivars grown under adequate (3.0 mM) and deficient (0.3 mM) K supply in hydroponics. Cultivars were grown for 4-5 weeks to study growth physiological parameters relating tolerance against K deficiency. Cultivars differed significantly in biomass production, shoot K concentration, uptake and use efficiency at both levels of K supply. Shoot and root biomass production was significantly decreased due to K deficiency stress. Reduction in shoot dry matter varied significantly among cultivars and efficient cultivars showed minimum reduction in shoot dry matter due to K deficiency. The result indicated significant genetic differences in K utilization efficiency among cotton cultivars which can be exploited for breeding efficient cultivars to be grown under low K soils especially in low input sustainable agriculture Keywords: Cotton, potassium, genetic variations, nutrient use efficienc
