Journal of Crops Improvement

Abstract In order to study the effect of N rate and plant density on grain yield and N use efficiency of blessed thistle, a field study ‎was carried out in a randomized complete block design with factorial arrangement of treatments in three replications‏ ‏at ‎Research Field of Tarbiat Modares University in 2013 and 2014 growing seasons.‎‏ ‏Treatments comprised of four pure N ‎rates (0, 50, 100 and 150 kg N ha-1)‎‏ ‏from urea source and five plant densities (5, 10, 15, 20 and 25 plants m-2).‎‏ ‏The main ‎effects of nitrogen and plant density were significant for grain yield, NUE, plant height, SPAD value, root to shoot weight ‎ratio and N content of grain. Increasing N rates increased grain yield, SPAD value, plant height and grain N, but agronomic ‎efficiency, N recovery and utilization were decreased by increasing of N rate; Higher densities resulted in decreased grain ‎yield and chlorophyll index, while improved NUE throughout increment of root to shoot weight ratio and plant height‏.‏‎ ‎Novel findings of this study could be used for N management. ‎