Effect of sowing time and nitrogen fertilizer rates on growth, seed yield and nitrogen use efficiency of quinoa (Chenopodium quinoa Willd) in Ahvaz, Iran

To study the effect of sowing time and nitrogen levels on growth, yield and nitrogen efficiency of quinoa cv. Titicaca, a field experiment was conducted at in 2017-2018 growing season research farm of Agricultural and Natural Resources Sciences University of Khuzestan, Ahvaz, Iran. The experiment was conducted in split plot arrangement in randomized complete block design with four replications. Experimental factors were four sowing dates (23 Sep., 12 Oct., 1 Nov. and 21 Nov.) assigned to main plots and five nitrogen rates (0, 80, 160, 240 and 320 kg.ha-1) randomized in sub plots. Analysis of variance showed that the effect of sowing date and nitrogen rate and their interaction effect were highly significant on all traits. Mean comparison showed that the highest number of seed.plant-1 (16915), biological yield (20064 kg.ha-1) and seed nitrogen content (3.67%) was observed in the sowing date of 23 Sep. and 320 kg.ha-1 nitrogen fertilizer. Also, the highest seed yield (8657 kg.ha-1), 1000 grain weight (4.26 g), harvest index (56.7%) and plant nitrogen content (2.80%) were observed at sowing date of 12 Oct. and 320 kg.ha-1 nitrogen. The lowest seed yield (381 kg.ha-1) was observed in sowing date of 21 Nov. and and no-application of nitrogen. With increasing nitrogen application from 80 to 320 kg.ha-1, nitrogen efficiency indices decreased. The highest seed yield of quinoa in Ahvaz can be achieved by sowing on 23 Sep. and 320 kg.ha-1 nitrogen.