Improving Plant Growth, Seed Yield, and Quality of Faba Bean by Integration of Bio-Fertilizers with Biogas Digestate

Exploring environmentally eco-friendly approaches to enhance crop growth and productivity are essential for sustainable agriculture. Therefore, a field trial was conducted during two growing seasons to study the effects of synthetic (nitrogen, N; phosphorus, P; and potassium, K), biogas digestate (BioD), bio-fertilizer (BioF), and their combinations on the growth, yield, and seed quality of faba bean (Vicia faba L.). The number of treatments was seven, as follows: control (zero NPK), NPK (30 kg N ha⁻¹; 45 kg P₂O₅ ha⁻¹: 48 kg K₂O ha⁻¹) as the recommended dose, BioD (2 t ha⁻¹), BioF (plant growth-promoting rhizobacteria; 1 kg ha⁻¹), 50% NPK + 50% BioD, 50% NPK + 50% BioF, and 50% BioD + 50% BioF. The results indicated that all fertilizer sources and their combinations improved the growth, seed yield, and quality of faba bean. However, the highest increase in plant height, leaf area, dry leaf weight, and stem dry weight of faba bean was recorded for the combined application of 50% BioD + 50% BioF. Moreover, the BioD +BioF fertilization enhanced the number of branches, number of seeds, 100 seed weight, and seed yield of faba bean. Similarly, BioD + BioF fertilization enhanced the total chlorophyll and N, P, and K contents of faba bean leaves. BioD fertilization also increased seed quality traits such as N, P, protein, and carbohydrate contents. The outcomes of BioD + BioF fertilization on growth yield and quality parameters of faba bean suggest that the concurrent application of biogas digestate with bio-fertilizer can reduce synthetic fertilizers.