Zn- and Cu-Doped MnFe₂O₄ Nanofertilizer: Synthesis, Characterization, and Their Role in Enhancing Fenugreek...

Micronutrient deficiencies and low nutrient-use efficiency remain critical constraints to sustainable crop production. This study tested the hypothesis that Zn- and Cu-doped MnFe₂O₄ spinel ferrite nanoparticles can function as an efficient multinutrient nanofertilizer to enhance fenugreek (Trigonella foenum-graecum L.) growth and physiological performance. Zn- and Cu-doped MnFe₂O₄ nanoparticles were synthesized via a sol-gel method and characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS). The nanoparticles exhibited a cubic spinel structure with an average crystallite size of 27 nm and uniform incorporation of Zn and Cu within the MnFe₂O₄ lattice. Foliar application at different concentrations (100-500 mg/L) significantly improved seed germination, seed vigor, plant height, leaf number, stem thickness, biomass accumulation, and chlorophyll content compared with the untreated control. The 300 mg/L treatment consistently produced the greatest improvements, increasing plant height, biomass, and total chlorophyll content by more than 25-40% relative to control plants. Higher concentrations of T₅ resulted in diminished benefits, indicating a concentration-dependent response. These findings demonstrate that Zn- and Cu-doped MnFe₂O₄ nanofertilizer provides a balanced and bioavailable source of essential micronutrients, offering a promising nano-enabled strategy for improving nutrient use efficiency and sustainable fenugreek production.