Document Type : Research Paper
Authors
1 Department of Plant Production Engineering and Genetics, Faculty of Agriculture, University of Kurdistan, Sanandaj, Iran
2 Department of Horticultural Science and Engineering, Faculty of Agriculture, University of Kurdistan, Sanandaj, Iran
Abstract
Objective: The excessive use of chemical fertilizers and agricultural pesticides has led to the accumulation of heavy metals in the soil, raising significant environmental concerns. Consequently, the adoption of biocompatible fertilizers to mitigate these risks is essential, particularly in low-yielding soils contaminated with heavy metals. Therefore, the present study aimed to investigate vermicompost's effect on alleviating arsenic's negative impacts on the morpho-physiological characteristics, yield and elemental content of the dragon’s head. Therefore, the present experiment was designed and conducted to investigate the effects of vermicompost application in mitigating the adverse effects of arsenic on the growth and physiological traits of the medicinal plant Lallemantia iberica (dragon’s head).
Methods: This pot experiment was conducted during the 2023–2024 growing season in the research greenhouse of the Faculty of Agriculture, University of Kurdistan. The study was arranged as a factorial based on a completely randomized design with three replications. The treatments included two levels of arsenic (0 and 25 mg/kg soil) and four levels of vermicompost (0, 5, 10, and 15% of soil weight). Sodium arsenate salt (NaH2AsO4) was employed to contaminate the growing medium. Morpho-physiological and biochemical traits, including stem and root length, shoot dry weight, chlorophyll and carotenoid content, membrane stability index, proline and soluble protein content, peroxidase enzyme activity, as well as macro- and micronutrient concentrations were evaluated at the flowering stage.
Results: The results of variance analysis of traits indicated the significant effect of different concentrations of vermicompost and arsenic application on most of the examined traits. The findings indicated that increasing arsenic levels in the soil, negatively affected growth characteristics (stem length 35%, root length 103% and plant dry weight 39%), photosynthetic pigment content (chlorophyll a 33%, chlorophyll b 40% and carotenoids 51%), and membrane stability index (23%), while proline content (33%), peroxidase enzyme activity (37%), and the concentrations of copper (36%), nitrogen (25%), and zinc (3%) increased. Application of vermicompost, particularly at a concentration of 15% by soil weight, significantly improved growth parameters (length Stem length 47%, root length 86% and plant dry weight 12%). It also enhanced photosynthetic pigment levels (total chlorophyll 87%, chlorophyll b 65% and carotenoid content 67%), increased soluble proteins content by 40%, and promoted nutrient uptake by the plants under both arsenic stress and control conditions.
Conclusion: Vermicompost (up to 15% of soil weight) reduces the negative arsenic application (concentration of 25 mg/kg soil) by improving the physicochemical conditions of the soil, improving its preservation and providing nutrients to the plant. The results also showed that, while in arsenic-contaminated soil, the plant has high arsenic absorption, but the application of vermicompost in the soil improves the growth and development of dragon’s head plant by increasing the absorption of other mineral elements compared to arsenic and reducing its toxicity in the plant.
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