Foliar application of molybdenum combined with cobalt affects leaf nitrogen concentration, grain yield, and yield components of soybean

Abstract The high protein content in soybean ( Glycine max (L.) Merrill) necessitates maximizing the nitrogen (N) absorption capacity and the biological N fixation process. This study aimed to evaluate whether foliar application of molybdenum (Mo) combined with cobalt (Co) enhances the productivity, yield components, N content, and protein and oil contents of soybeans. The experiment consisted of randomized blocks with a split‐plot arrangement, with two soybean cultivars (BRS 399 Roundup Ready [RR] and BRS 284) as a main plot and the presence or absence of foliar application of Co + Mo as a subplot, during two seasons and eight replications. Foliar application was performed during the vegetative stages V3 and V5. The results revealed that foliar fertilization with Co + Mo increased the grain yield by 9.8% for BRS 399 RR in the first season and by 15.4% for BRS 284 in the second season. For BRS 399 RR, the N concentration in the leaves, protein yield, and oil content were also positively affected by the Co + Mo application. For BRS 284, only the N concentration in leaves increased in the first season, whereas the protein yield improved in the second season. However, compared with the control, the protein and N concentrations in the grains of both cultivars and seasons were not significantly influenced by Co + Mo application. The foliar application of Co + Mo had both positive and neutral effects on grain yield, protein yield, and leaf N concentration, depending on weather conditions and the soybean cultivar used, thus impacting N use efficiency.