چكيده لاتين :
Introduction Safflower (Carthamus tinctorius L.) is one of the drought-resistant oilseed plants. Due to its specific morphological characteristics, it has the ability to produce proper oil in Iran's climate, and some of its varieties have up to 45% oil content (Moradi et al, 2017). One of the most important restrictions on production of crops in most parts of Iran is lack of water. In these areas, due to rainfall fluctuations, some of the important stages of plant growth has been affected by potential degradation of soil (Omidi et al, 2012). Production of crops in arid and semi-arid areas requires the use of drought-resistant plants to have acceptable yields with minimal moisture content (Khalili et al., 2014).
Materials and Methods In order to investigate the effect of deficit- irrigation in reproductive stage on grain yield, yield components, and oil percentage of safflower cultivars, an experiment was conducted at Research Farm of Islamic Azad University, Birjand Branch, in 2015-2016. The study was conducted in split plots in a completely randomized block design with three replications. The main factor included three levels of irrigation at the reproductive stage (7, 14 and 21 days) and the sub-factor included three varieties (Padideh, Goldasht and KWS). Each sub plot consisted of 6 planting lines with a length of 6 meters and a row spacing of 0.5 meters, with two lateral rows on each side of each plot as margin. The distance between sub plots was 0.5 m, between two main plots were 1 m and between two repetitions were 3 m. The land preparation operations began in early fall. Based on soil test results, 150 kg ha-1 urea (one third before planting, one third in stem elongation, and one third in pre-flowering stage), 120 kg ha-1 triple superphosphate and 100 kg ha-1 potassium sulfate before planting was spread in the ground and mixed with soil. Seeds were planted by hand in November. The evaluated traits in this study included plant height, number of branches, number of capitulum per plant, number of seeds per capitulum, kernels 1000 weight, grain yield, biological yield, harvest index, oil percentage and oil yield. After data collection, statistical analysis was performed using MSTATC software. To compare the means, Duncan's multiple range test was used at a 5% probability level.
Results and Discussion The results showed that increasing the irrigation interval from 7 to 14 days had no significant impact on the studied traits, but increasing the irrigation interval from 7 to 21 days reduced the number of seeds per head (22.5%), kernels 1000 weight (12.41%), grain yield (7.78%), biological yield (11.41%) and oil yield (19.25%). Going from the vegetative stage to reproduction stage, water restriction reduced the the durability of the leaf area index. It leads to a further reduction in photosynthesis, and due to the fact that at that time grains are increasing in number and weight, the filling period of seeds and grain weight decreases. Ultimately, this leads to a decrease in grain yield. All studied traits (except number of seeds per capitulum) were affected by cultivars. The highest oil content was obtained by both KWS cultivars (33%) and Padideh (30.7%). Goldasht and KWS cultivars had the highest grain yield (1868 and 1768 kg ha-1, respectively) and oil yield (521.2 and 58.43 kg ha-1, respectively). Also, among the grain yield components, the weight of one thousand grains had a positive and significant correlation with grain yield.
Conclusions The results show that in order to save water, 14 days irrigation stages and Goldasht and KWS cultivars are suitable in the breeding stage of safflower in Birjand region.
