Effect of Different Levels of Phosphorus on Growth, Yield, and Phosphorus Uptake Efficiency in Safflower Cultivars

In order to determine the efficiency of different safflower (Carthamus tinctorius L.) cultivars in terms of their uptake and response to phosphorus fertilizer application, a 2-year (2016-2018) experiment was conducted in a randomized complete block design as 2 x 5 factorial with three replications at the Arak Agricultural Research Center Station. Treatments included two cultivars of Sina and Padideh and five levels of phosphorus (0, 25, 50, 75 and 100 kg.ha-1) as triple superphosphate. The results of analysis of variance showed that grain yield, number of bolls, 1000-seed weight, phosphorus, nitrogen, and potassium uptake, and total phosphorus yield were affected by the effect of cultivar and phosphorus levels. Apart from the total dry matter weight and phosphorus concentration, other studied characteristics were affected by the year. Plant height and nitrogen concentration were affected only by cultivar, while total dry matter weight and phosphorus concentration were affected by phosphorus levels. Comparison of the mean effect of phosphorus levels on grain yield showed that the maximum grain yield in both cultivars was obtained in treatment of 25 kg P/ha. In terms of total phosphorus efficiency, the level of 50 and in terms of phosphorus grain uptake efficiency and phosphorus-stress factor the level of 25 kg P/ha were optimal. Phosphorus efficiency indices did not differ significantly between the two cultivars, but Sina cultivar showed higher phosphorus uptake than Padideh.