Document Type : Research Paper - Agroecology
Authors
1 Department of Agronomy and Plant Breeding, Faculty of Agriculture, Yasouj University
2 Professors of Department of Agronomy and Plant Breeding, Faculty of Agriculture, Yasouj University
3 Professor, Department of Agronomy and Plant Breeding, Faculty of Agriculture, Yasouj University
Abstract
Abstract
Introduction: Safflower (Carthamus tinctorius L.) is a multipurpose plant with medicinal and oil applications, primarily cultivated for edible oil and industrial dyes. Water resource limitations in Iran and drought stress negatively affect the growth and performance of this plant. Sulfur, as the fourth most consumed nutrient for plants, plays a vital role in photosynthesis and cell membrane structure. Excessive use of chemical sulfur fertilizers can lead to soil salinity. Therefore, bio-fertilizers have been proposed as a suitable alternative. Thiobacillus spp. bacteria help improve plant growth by providing sulfate and enhancing soil properties.
Materials and methods: This study was conducted to evaluate the effect of chemical and biological sources of sulfur, including bentonite sulfur and Thiobacillus bacteria, on the content of elements (N, P, K, S, Fe and Zn) of aerial organs, some physiological characteristics, and the seed yield of safflower under water stress conditions in the summer of 2023 in the research farm of Yasouj University Faculty of Agriculture located in Dashtrom. The experiment was performed as a split factorial based on a randomized complete block design with three replications. Irrigation regimes at three levels (complete irrigation and interruption of irrigation from the beginning of flowering and the beginning of seed filling) were the main factor, and the combination of bentonite sulfur fertilizer at three levels (0, 150, and 300 kg/ha) and Thiobacillus bacteria at two levels (use and non-use) were the secondary factors studied.
Results and discussion: Statistical analysis showed that bentonite sulfur fertilizer and the use of Thiobacillus bacteria, significantly improved the content of aerial organ elements, physiological traits, and grain yield of safflower under drought stress. Under severe dehydration conditions (cut off irrigation from flowering stage), the highest content of elements of aerial organs, including nitrogen (2.33%), sulfur (0.149%), iron (44 mg/kg), and zinc (25.66 mg/kg), was obtained from the simultaneous application of 300 kg of bentonite sulfur + Thiobacillus bacteria. The triple interaction of irrigation regime × bentonite sulfur × Thiobacillus was also significant for traits such as total chlorophyll content, carotenoid content, total soluble sugars, and activity of antioxidant enzymes catalase and peroxidase. The highest of this these traits in each irrigation regims were observed in application of 300 kg/ha of bentonite sulfur + Thiobacillus. The content of malondialdehyde increased by cutoff irrigation from the stages of flowering and seed filling, but it decreased with the use of bentonite sulfur and Thiobacillus bacteria.The grain yield was also affected by the application of 300 kg/ha of bentonite sulfur + Thiobacillus under full irrigation and medium stress levels, with an increase of 25.28% and 45.54%, respectively.
Conclusion: The findings of this research indicate that the application of water stress, particularly from the flowering stage, was associated with a decrease in physiological traits and seed yield of safflower. The application of 150 kg/ha sulfur-bentonite along with Thiobacillus bacteria, in addition to reducing the use of chemical fertilizers and its negative consequences, led to increased nutrient uptake, improved efficiency of biofertilizer, and enhanced seed yield under water stress conditions.
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