Experiment were conducted with sorghum (Sorghum bicolor (L.) Moench) to a) determine optimum conditions to screen for differential responses of genotypes to Fe deficiency in nutrient solutions, b) compare responses of nutrient solution-grown plants to soil-grown plants, and C) determine some of the physiological and chemical properties of genotypes consiedered to be both tolerant and susceptible to Fe deficiencies. Plants were grown in nutrient solutions and soils under growth chamber and greenhouse conditions. Iron deficiencies were imposed on the plants by 1) adding varied amounts of Fe, 2) adding higher than normal levels of P, 3) adding high levels of CaCO3, 4) using different sources of N, and 5) using low Fe soils. Parameters used to measure some aspectsof different responses of the genotypes to Fe and the physiological and chemical properties were the degree Fe deficiencysymptoms in the upper leaves, dry-matter yields, dry-matter produced/unit Fe, Fe concentration and contents, top/root dry-matter and Fe ratios, distribution of Fe among upper and lower leaves, Ph changes innutrient solutions, 'reductant' (phenolic compounds) released by roots in nutrient solution, leaf surface areas and plant heights, leaf chlorophyll concentrations, and concentrations of P, K, Ca, Mg, S, Mn, Cu, and Zn and their possible interactions with Fe in leaves and roots. In nutrient solution screening, plants grown with higher than normal P and with N03 as the sole source of N become Fe deficient more rapidly and gave wider (...).