Interactive effects of soil salinity and N fertilizer on stargrass (Cynodon plectostachyus (K. Schum.) Pilger) growth and N metabolism were investigated. Nitrogen contents were partitioned to study the effects of substrate salinities on hydrolysis of protein‐N and the accumulation nonprotein‐N assimilates. Mixed chloride‐sulfate solutions of the same ionic ratios and electrical conductivities (EC) of 4.8, 9.6, and 14.4 mmhos/cm were equilibrated with Brennan fine sandy loam (Typic Haplustalf) soil, after which N was applied in a factorial arrangement at rates of 0, 67, 133, and 200 mg/kg of soil.Nitrogen fertilizer interacted significantly with soil salinity to stimulate dry matter and protein‐N yields at the 4.8‐mmhos/cm level. No evidence of a toxic nonprotein‐N accumulation in plant tissue was observed even with high N fertilization at this salinity level. The 9.6‐mmhos/cm salinity treatment was considerably more deleterious to dry matter than to protein‐N production processes. Dry matter production and protein‐N synthesis were severely inhibited at the 14.4.mmhos/cm salinity level although NO3‐N appeared to be adequately absorbed and reduced.