Effectiveness of biostimulants on growth, yield, and seed nutrient content of faba bean (Vicia faba L.) grown on two contrasting soil types

Faba bean is the main source of protein and minerals for most of Ethiopia's population. However, soil fertility challenges production, and good agricultural practices are needed to increase yield and nutritional value. Pot and field experiments were conducted to evaluate the effect of the sole and combined application of biostimulants on faba bean growth, yield, and seed nutrient content. Effects of sole and/or combined applications of plant growth-promoting rhizobacteria (PGPR) (Bacillus subtilis, Pseudomonas fluorescens, and Rhizobium leguminosarum) and moringa leaf extract (MLE) were pre-evaluated under greenhouse conditions. Subsequently, selected treatments from this pot experiment were further evaluated on a local and Moti faba bean variety under field conditions on Nitisol and Vertisol. The biostimulant treatments significantly improved faba bean growth under greenhouse conditions. However, they did not influence the crop's growth, yield, and seed nutrient content under field conditions. Varieties significantly (p < 0.05) influenced yields and yield components obtained from Vertisol, as well as seed micronutrient contents from both soils. A local variety was found to have higher nutrient content. Meanwhile, grain yield had a positive correlation with seed iron (Fe) content and a negative correlation with seed selenium (Se) and phosphorus (P) contents. In addition, seed Se content strongly correlated with P content. From this study, it could be concluded that using biostimulants does not help in improving faba bean attributes under field conditions. However, further examination of a wider range of biostimulants under field conditions is required to uncover their realistic effectiveness for bean crop biofertilization.