Barbieri, P. A., Echeverría, H. E., Sainz Rozas, H. R. and Andrade, F. H. 2013. Nitrogen status in maize grown at different row spacings and nitrogen availability. Can. J. Plant Sci. 93: 1049-1058. Improving nitrogen use efficiency (NUE) is imperative to sustainable agriculture. To attain this goal in maize crops (Zea mays L.) there are nitrogen (N) diagnosis methods that enable determination of a crop's nutritional status by analysis of plant parts. Maize planted in narrow rows (NR) can have increased dry matter (DM), grain yield and accumulated N. However, no reports have been found on the effect of NR of N in plant diagnosis methods. An experiment was performed over 3 yr to evaluate NR and N fertilizer rates on the N dilution curve, N concentration in grain and chlorophyll content in maize. Treatments consisted of a factorial combination of row width (70, 52 and 35 cm) and N rate (0 to 180 kg N ha^-1). The N dilution curves adjusted for fertilized or control treatments were similar among row spacing. Nitrogen concentration in grain was correlated with relative yield (RY), and similar critical values for N response were similar between row spacings. Leaf chlorophyll content increased with N and NR; however, green index (GI) and N sufficiency index (NSI) values were not different between row spacing when correlated to RY. These results indicate that response thresholds to N fertilization determined on plant tissue for NR treatments were similar among row spacings. Thus, there is no need to adjust the response thresholds to N application based on row spacing, as NR did not cause any changes in physiological efficiency (PE) due to the determined proportional increases, both in accumulated N in DM and grain yield.