the nitrification inhibitor, dicyandiamide (cyanoguanidine) (dcd), can improve fertilizer n efficiency; however, yield reductions and phytotoxicity from the use of dcd have been reported a greenhouse experiment was designed to determine the effect of dcd on growth, chlorophyll concentration and nutrient concentration of corn (zea mays l. ), cotton (gossypium hirsutum l. ), and grain sorghum $left bracket$ sorghum bicolor (l. ) moench. $right bracket$ . dicyandiamide-n/urea-n combinations were applied to pots containing a norfolk sandy loam (fine-loamy, siliceous, thermic, typic paleudults) cropped to each of the three species. increasing the proportion of n as dcd decreased plant dry weight and leaf chlorophyll concentration and increased stem-leaf n concentrations nitrogen recovery decreased curvilinearly from 103 to 4, from 64 to $minus$ 6, and from 72 to 4 for corn, cotton, and sorghum, respectively, with increasing proportion of n as dcd-n. the effects of dcd-n on stem-leaf tissue concentrations of p, k, ca, mg, fe, mn, zn, and cu varied with dcd-n concentration, plant species, and nutrient element. (edited author abstract) 23 refs