Nutrient and heavy metal profiling of Teff (Eragrostis tef) under water hyacinth compost and fertilizer treatments using UV-Vis spectroscopy and flame atomic absorption spectroscopy (FAAS)

Eragrostis tef (Zucc.) Trotter , commonly known as teff, is a staple cereal crop in Ethiopia, prized for its high nutritional content and deep cultural significance. However, increasing soil contamination from synthetic agricultural inputs threatens on food safety. Exploring sustainable soil amendment alternatives is therefore critical. Composting the invasive aquatic weed (water hyacinth) offers a dual benefit of environmental management and potential soil fertility. This study was conducted to evaluate the nutritional quality and toxic metal profiling. Thirteen grain samples from each treatment plot were analyzed for key macronutrients (N, C, P, S), essential metallic nutrients (Mg, K, Ca), and trace metals (Fe, Mn, Zn, Cu, Cr, Ni, Pb, Cd) using standard UV-Visible Spectrophotometry and Flame Atomic Absorption Spectroscopy (FAAS). Method validation through spiking indicated reliable analytical performance (recoveries: 80–120%). Nutrient contents showed significant variation across treatments, with nitrogen (0.333–0.349%), phosphorus (56.07–64.27%), sulfur (29.98–42.89%), and organic carbon (75.58–83.01%). Among metals, magnesium was most abundant (2093.1–3255.1 mg/kg), followed by potassium, calcium, iron, and zinc. These findings highlight the potential of water hyacinth compost to enhance soil fertility without compromising grain quality, offering a sustainable strategy for improving the nutritional profile and environmental safety of teff cultivation.