Application of Bio-Fertilizers Improves Forage Quantity and Quality of Sorghum (Sorghum bicolor L.) Intercropped with Soybean (Glycine max L.)

In recent years, application of bio-fertilizers (BFs) in intercropping systems has become known as one of the main sustainable and eco-friendly strategies for improving the quantity and quality of forage crops. In order to evaluate the forage quantity and quality of sorghum intercropped with soybean, a two-year field experiment was carried out as factorial based on a randomized complete blocks design (RCBD) with three replications. The first factor was different cropping patterns including soybean monocultures with densities of 40 and 50 plants m−2 (G40 and G50), sorghum monocultures with densities of 10 and 15 plants m−2 (S10 and S15) and intercropping of two plants with the mentioned densities. The second factor was non-application (control) and application of bio-fertilizers. The results demonstrated that the highest dry forage yield of sorghum (21.22 t ha−1) was obtained in monoculture conditions with density of 15 plants m−2 and inoculation with bio-fertilizer (S15+BF). The maximum crude protein (CP = 149.6 g kg−1 DM), ash (113.2 g kg−1 DM), water soluble carbohydrates (WSC = 251.16 g kg−1 DM), dry matter intake (DMI = 26.83 g kg−1 of body weight), digestible dry matter (DDM = 668.01 g kg−1 DM), total digestible nutrients (TDN = 680.42 g kg−1 DM), relative feed value (RFV = 142.98%) and net energy for lactation (NEL = 1.625 Mcal kg−1) were observed in the intercropping of S10G50 inoculated with BF. Interestingly, application of bio-fertilizers enhanced the content of CP, ash, WSC, DMI, DDM, TDN, RFV and NEL by 7.5, 8, 11.7, 3.6, 2.3, 12.3, 5.9 and 3.5% when compared with the control (non-application of bio-fertilizers). In all intercropping patterns, the total land equivalent ratio (LER) value was greater than one, representing the advantage of these cropping patterns in comparison with sorghum monoculture. The highest total LER was recorded in the intercropping of S15G40 and S10G50 following application of BF. Additionally, the highest monetary advantage index (MAI) was calculated in the intercropping of S15G40+BF. Generally, it can be concluded that the intercropping of S10G50 along with bio-fertilizer inoculation could be suggested as an eco-friendly strategy for improving the forage quantity and quality under low-input conditions.