Effects of drought stress and fertilizer sources on yield and yield components of safflower (Carthamus tinctorius L.)

In order to study the effect of different drought stresses and fertilizer sources on yield and yield components of safflower (Carthamus tinctorius L.), a field experiment was conducted as split plot based on randomized complete block design with three replications at the Agricultural Research Station, college of Agriculture, Urmia University, Iran during growing season of 2009-2010. Treatments consisted of well-irrigation (I1), irrigation only at vegetative growth stage (I2), and irrigation only at reproductive growth stage (I3) as main plots and fertilizer sources including control (C), Urea (U), Humix as organic fertilizer (O), biofertilizes of Nitroxin (N), Biosoulphoure (B), integrated fertilizer treatments (Urea + Humix + Nitroxin) (T1), and (Urea + Humix + Biosoulphoure) (T2) as sub plots. The results indicated that the head number per plant, 1000-seed weight and oil content were significantly influenced by "Water deficit stress × fertilization" interaction. The most number of head per plant (18.3) obtained in I1T2 and the least (10.4) observed in I2U treatment. The highest (44.7 g) and lowest (32.05 g) 1000-seed-weight was obtained in I3T2 and I1O treatments, respectively. I1B and I3C treatments had the maximum and minimum oil contents, respectively. The greatest amount of biological yield (8819.6 kg.ha-1) obtained from I1, while the lowest was observed in I2 treatments. Seed weight per head and seed yield were the highest and lowest in I1 and I2 irrigation treatments, respectively. Plants treated with T2 and control fertilization treatments had the highest (2830 kg.ha-1) and the lowest (1845.4 kg.ha-1) seed yield, respectively. Generally, water deficit stress in reproductive growth stage caused the greatest reduction in most of the traits associated with yield and yield components of safflower. Among the fertilizer sources, integrated fertilizer treatments (Urea + Humix + Biosoulphoure) had the most effect on safflower.