Six greenhouse pot experiments were conducted in which yield and nutrient uptake responses of corn(Zea maysL.) or tall fescue(Festuca arundinaceaShreb) to N, P, K, lime, or temperature variables were measured. This paper describes yield—NO3‐N and total N concentration trends in these experiments. Crop concentrations of total N and NO3‐N during early growth increased consistently with amount of applied N. These concentrations usually decreased (by dilution and assimilation) with time of growth and yield response to other growth‐limiting nutrients and other factors. Concentrations of K also increased in corn with amount of applied K, and high K was associated with higher concentrations of NO3‐N during early growth in some experiments. This was usually true only for early crop growth periods during which rates of nutrient uptake exceeded growth rate. High K concentrations may have retarded growth and NO3‐N reduction and assimilation.