Investigation of Rate and Method of Nitrogen Application on Nitrogen Use Efficiency and Seed Yield of Safflower (Carthamus tinctorius L.)

Nitrogen fertilizer management has a special priority for safflower economic production. Increasing the efficiency of this element, in addition to increasing economic benefits, also reduces environmental pollution. Therefore, a factorial experiment was conducted in the form of statistical design of complete randomized blocks with three replications at Safiabad Agricultural and Natural Resources Research and Education Center during two years (2012 and 2014). Experimental treatments included four amounts of pure zero  nitrogen control (without nitrogen application), 60, 120 and 180 kilogram per hectare and four levels of nitrogen application time as split (consumption of all when planting T1, consumption of two thirds when planting and one third the beginning of the stem elongation T2, consumption of one third when planting and two thirds of the beginning stem elongation T3 and consumption of one third during planting, one third of the beginning of stem elongation and one third of early flowering T4 ). The results showed that the interaction of treatments on plant height, number of fertility heads per meter square, seed yield, oil yield, use efficiency and nitrogen uptake by seed were significant. The main effect of nitrogen on the number of seeds per head, one thousand seed weight, oil percentage and nitrogen uptake efficiency were significant. Also, the main effect of split on the number of seeds per head, oil percentage and nitrogen uptake efficiency was significant. The interaction of treatments compared to control treatment (without nitrogen application) showed an increase in seed yield and consequently oil yield. On the other hand, with increasing nitrogen application compared to control treatment and also with its two and three stages split (T2, T3 and T4) nitrogen efficiency indices decreased and increased, respectively. Therefore, according to the conditions of this experiment and the calculation of the ratio of benefit to cost, application of 60 kiligram pure nitrogen per hectare one-third at a time (T4) with seed yield of 2226 kilogram per hectare and  the highest ratio of benefit to cost (43.18) and nitrogen use efficiency (31 kilogram per kilogram) is recommended.