| چکیده انگلیسی مقاله |
Background and Objective: Drought stress is one of the most critical factors influencing agricultural production, particularly in irrigated farming systems in arid and semi-arid regions of the world. Organic fertilizers can mitigate the detrimental effects of drought stress on medicinal plants. Developing new management strategies is essential to alleviate the negative impacts of drought. Among the most effective approaches to plant nutrition management under drought conditions is the use of organic fertilizers, which significantly contribute to sustainable agriculture advancement and expansion. Therefore, this study aimed to investigate the effects of different organic fertilizers in the cultivation medium of black seed and their influence on physiological traits and seed yield under various irrigation intervals.
Methodology: This experiment was conducted using a completely randomized block design with two factors and three replications. The first factor included four irrigation regimes: 20%, 40%, 60%, and 80% depletion of field capacity moisture. The second factor involved planting beds composed of different organic materials at 5% (w/w) of pot soil, including normal soil (control), normal soil + biochar, normal soil + compost, normal soil + vermicompost, and normal soil + animal manure. Each pot contained six kilograms of soil. Initially, the soil was passed through a 2 mm sieve, and organic fertilizers were manually mixed with the soil in each pot at a rate of 5% by weight. On February 19, black seeds were sown in plastic pots, with fifteen seeds per pot. Two weeks after sowing, at the three-leaf stage, seedlings were thinned to six plants per pot. After planting, all pots were irrigated uniformly. Upon the emergence of black seed plants and at the four- to five-leaf stage, irrigation treatments were applied based on the designated moisture depletion levels (20%, 40%, 60%, and 80%). Measured plant responses included leaf nitrogen, phosphorus, and potassium content; ion leakage; relative water content; malondialdehyde concentration; chlorophyll a and b content; and catalase and peroxidase enzyme activities. Finally, variance analysis was conducted, and means were compared using Duncan’s multiple range test.
Results: The findings indicated that increased drought stress led to reduced nitrogen, phosphorus, and potassium content in the leaves. Conversely, the highest concentrations of these nutrients were observed under treatments with normal soil + vermicompost or animal manure. Rising drought stress also reduced leaf relative water content; specifically, irrigation at 40%, 60%, and 80% moisture depletion led to significant reductions of 7%, 15%, and 32%, respectively, compared to 20% moisture depletion. At 60% depletion, compost, vermicompost, and animal manure treatments significantly reduced ion leakage by 11.8%, 14.5%, and 12.2%, respectively. Under 80% depletion, compost, and vermicompost significantly decreased malondialdehyde levels by 15.2% and 17.8%, respectively, relative to the control. At 20% and 60% depletion, the highest total chlorophyll content was observed in normal soil combined with vermicompost, followed by animal manure and compost. Catalase and peroxidase activities increased progressively with drought severity. At 80% depletion, the dry weight of aerial parts increased by 46% and 56% in the animal manure and vermicompost treatments, respectively, compared to the control. Likewise, grain weight increased by 26% and 32% under these treatments at the same drought level.
Conclusion: The results demonstrated that drought stress adversely affected black seed plants' nutrient concentration and physiological traits. Applying normal soil with vermicompost or animal manure effectively enhanced photosynthetic pigment levels, promoting plant growth. Compared to vermicompost and animal manure, biochar, and compost had a relatively lower impact on improving grain yield. Overall, vermicompost and animal manure are recommended for cultivating black seed under varying humidity conditions. |