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.