Abstract
This study evaluates the combined effects of cobalt (Co) application and nitrogen (N) fertilization on faba bean (Vicia faba) growth, yield, and nutritional quality under field conditions during the 2021/2022 and 2022/2023 growing seasons. Field experiments were conducted at the Research and Production Station in El-Nubaryia, Egypt, using a split-plot design with three replicates. Nitrogen fertilizer levels (100%, 75%, 50%, and 25% (NH₄)₂SO₄) were applied to main plots, and cobalt concentrations (with and without 12 ppm) were applied to subplots. Cobalt treatment significantly enhanced root nodule formation, nitrogenase activity, and overall plant growth, especially under higher nitrogen levels. The highest positive effects on nodulation, yield components (such as number of pods and seed yield), and nutritional content (N, P, K, Mn, Zn, Cu) were observed at 100% nitrogen, followed by 75% and 50% nitrogen treatments. The results indicated that spraying with cobalt with 75% nitrogen fertilization was better or equal to 100% nitrogen fertilization without cobalt, which saves 25% of nitrogen fertilization. Cobalt improved faba bean productivity and nutrient content, particularly when combined with optimal nitrogen levels, suggesting its potential role in sustainable agriculture. The study underscores the beneficial impact of cobalt and nitrogen synergy in enhancing crop productivity and nutritional value.