Physiological and Biochemical Responses of Fenugreek (Trigonella Foenum-graecum L.) to Arsenic Stress and Organic Fertilizer Amendments

The contamination of soil and water with arsenic (As), brought about by both natural occurrences and human actions, presents a significant environmental problem on a worldwide scale. The primary objective of this research was to explore how organic fertilizers could help reduce the harmful effects of As on fenugreek plants. This study employed a completely randomized factorial design to investigate the effects of four fertilizer treatments—vermicompost (VC) at 25% w/w, vermicompost tea (VCT) at 5 ml l⁻¹, seaweed extract (SWE) at 5 ml l⁻¹, and biochar (BC) at 30% w/w—under three As concentration levels (0, 25, and 50 mg kg⁻¹ soil). Increased levels of As (0 to 50 mg kg⁻¹) were found to negatively affect yield and growth metrics, but all fertilizers were able to reduce these impacts under As stress. Stress-induced increases in proline, lipid peroxidation, flavonoid and vitamin C contents, and activity of antioxidant enzymes were observed, and the application of fertilizer treatments further enhanced these responses. Reduced relative water content (RWC), membrane stability index (MSI), carbohydrate content, PSII photochemical efficiency, and photosynthetic pigment contents under As stress were improved by fertilizer treatments. Fertilizers counteract the decline in macro- and microelement contents caused by stress, leading to increased accumulation of elements in leaves. Multivariate analysis revealed a close association between physiological and biochemical traits and fertilizer treatments. This suggests that all organic fertilizer treatments have a generally positive influence on the investigated traits, irrespective of As concentrations. This study suggests that all fertilizer treatments can alleviate the harmful effects of As exposure on fenugreek plants. Given the global challenge of heavy metal stress, our findings underscore the significance of tested organic fertilizers as cost-effective solutions for mitigating their adverse effects.