Effects of Sowing Date and Limited Irrigation Water Stress on Spring Safflower (Carthamus tinctorius L.) Quantitative Traits

Deficit irrigation is an optimization strategy in which irrigation water applied during drought-sensitive growth stages of a crop. This study was carried out to determine the effect of sowing date and limited irrigation water stress on quantitative characters of spring safflower cultivar (Arak 2811) grown in Agricultural Research Centre of Faculty of Agriculture and Natural Resources of Tehran University, in Karaj, Iran, during 2008 and 2009. The treatments comprised three sowing dates as main plots and limited irrigation treatments as subplots. The evaluated traits in this study were plant height, heads number and seed number per head, 1000 seed weight, seed yield, biological yield and harvest index. Interactive effects of sowing date and limited irrigation water stress indicated that plant response to irrigation is depended on the sowing date. Early sowing date and normal irrigation treatments at various safflower growth stages were identified maximum for all traits and minimum for the cut irrigation in the last sowing date at heads forming, flowering and grain filling stages, respectively.Under these conditions, optimal sowing date and irrigation application for safflower at reproductive stages could be a great management option to lessen the negative aspects of temperature and drought stress.