Introduction: Arsenic is toxic to plants and accumulates in minute quantities within the majority of species. The amount of arsenic absorbed by a plant is contingent upon its source and solubility (Gonzalez et al., 2021). Arsenic mobility and availability are strongly influenced by soil type, pH, and the use of chemical fertilizers such as phosphorus and potassium. Arsenic and phosphorus share chemical similarities and compete for carrier and membrane carrier absorption (Taati et al., 2021). Basil was chosen for this study due to its rapid growth and ability to absorb contaminants such as heavy metals.
This study's objective was to use phosphorus and potassium fertilizers to reduce the toxicity of arsenic and optimize basil growth in arsenic-contaminated soils. The effects of varying concentrations of arsenic, phosphorus, and potassium, as well as their interactions, on arsenic toxicity, crop growth, phosphorus and potassium uptake, and arsenic accumulation in two basil cultivars were investigated.
Materials and Methods: This study was conducted in the greenhouse of the University of Zabol during the winter of 2013 and the spring of 2014. Two seed cultivars, Keshkeni Luvelou and landrace of Zabol, constituted the first factor, while types of fertilizers, including 50, 150, and 250 mg of phosphorus and potassium per kg of soil for triple superphosphate and potassium sulfate, constituted the second factor. Arsenic sulfate was added to all containers at a constant rate of 15 mg per kilogram of soil. Plant height, number of lateral branches, number of leaves, fresh weight of shoots, and arsenic concentration in plant shoots were measured. The number of leaves per plant, the number of lateral branches per plant, the height of the plant, the diameter of the main stem, the length of the roots, and the fresh weight of the plant were also measured. After harvesting the plants, they were separated into shoots and roots, dried, and weighed. To measure the heavy metal arsenic, plant samples were dried and ground using the dry digestion method. The arsenic concentration in the extract was determined using atomic absorption spectrometry.
Results and Discussion: Results indicated a 1 percent level of significance for cultivar effects on plant height, number of leaves per plant, number and length of lateral branches, fresh weight, and leaf area. In all growth-related characteristics, the local cultivar differed significantly from the modified cultivar. The addition of arsenic decreased plant growth and increased arsenic concentration in plant organs. The study of the relationship between phosphorus and arsenic revealed that in both cultivars studied, the concentration of arsenic in the shoot decreased as the amount of phosphorus increased. In the interaction between arsenic and potassium, the most arsenic was found in the aerial portion at the lowest potassium concentration. The landrace of Zabol grew better than the modified cultivar due to its adaptation to the local environment. The results of the control treatment on both cultivars revealed that only the addition of arsenic at a concentration of 15 mg/kg soil can inhibit plant growth in comparison to other fertilizer applications. This could be due to the absence of heavy metal contamination in the region, as studies have shown that arsenic can cause stress in plants and inhibit their growth. It can be said that the interaction of phosphorus and potassium with arsenic in other treatments mitigates the negative effect of arsenic on the landrace, whereas the modified cultivar exhibited a type of growth stimulation.
Conclusion: By acting on arsenic absorption, phosphorus and potassium fertilizers can reduce the concentration of this substance in plant food, thereby reducing the risk of toxicity. In the interaction between phosphorus and arsenic, as the amount of phosphorus used increased, the concentration of arsenic in the plant's shoots decreased, indicating competition for absorption. At low phosphorus and potassium levels, soil arsenic uptake increased. Landrace of Zabol was superior to breeding cultivar in the majority of vegetative traits, which can be explained by the greater compatibility of breeding cultivar with regional conditions. Landrace of Zabol absorbed less arsenic in the control treatment; however, arsenic had a significantly negative effect on the growth of this cultivar compared to other treatments. In contrast to the landrace, in the control treatment of Keshkeni Luvelou, low concentrations of arsenic stimulated plant vegetative growth.