Substantial tracts of fallow farmland remain unutilized across southwestern China throughout winter and spring. To explore a high-yield planting pattern for utilizing such fallow land, a cereal–legume intercropping experiment was conducted in Chengdu in 2021–2022 and in 2022–2023. This involved five different intercropping ratios of oat (Avena sativa) and common vetch (Vicia sativa) including 100:0, 75:25, 50:50, 25:75, and 0:100 based on seed number per unit area. The relative density, LER (land equivalent ratio), hay yield, nutritional composition and in vitro fermentation characteristics were assessed. The study revealed that the combination of oat and common vetch led to a significant enhancement in the production performance over the monocultures. At the flowering stage, the most balanced interspecific competition was observed at a ratio of 50:50. The ratio of 50:50 had the higher LER in the mixture—from 1.018 to 1.873—, which was significantly higher than the other two intercropping ratios in 2021–2022. At the flowing development stage in 2021–2022, the harvesting of mixed crops at the 50:50 ratio resulted in a significant higher crude protein yield, 1454.7 kg/hm2, than the other intercropping ratios. As the growth stage continued, the mixture hay neutral detergent fiber and acid detergent fiber contents increased, while the relative feed value and crude fat content decreased. The soluble sugar content increased with the prolongation of the growth stage and peaked at the jointing stage, and decreased with the decrease in the proportion of oat in the mixture. Additionally, the gas production showed an overall decreasing trend with the increase in the proportion of common vetch. The dry matter degradation rate in the mixture hay was overall higher than that of the monocultures, and the NH3-N content showed an overall trend of increasing with the decrease with the intercropping ratio of oat. Consequently, the 50:50 ratio may be recommended as an oat-common vetch intercropping ratio suitable for utilizing fallow fields in southwestern China from October to April to produce high-quality forage.
Fang et al. (Thu,) studied this question.