Cultivar and growing degree day accumulation effects on forage partitioning, quality attributes, and nutrient yields, and water use efficiency of common vetch on the Tibetan Plateau

The use of common vetch in smallholder crop-livestock systems has expanded widely in recent years, partly to relieve grazing pressure and improve seasonal supply of high-quality herbage. The aim of this work was to evaluate plant fraction biomass accumulation, forage quality attributes and nutrient yields, and water use efficiency (WUE) responses of a local and an improved cultivar of common vetch in a two-year study on the Tibetan Plateau. No differences were observed between the cultivars for dry forage yield, nutrient yields, and WUE. Regressions of forage quality attributes and nutrient yields on growing degree days were explained and coefficients of determination were high in all cases (R² ≥ 0.833). These results demonstrate that air temperature information can be a useful tool for understanding forage quality attributes and nutrient yields of common vetch. The models from this study also provided in-field estimation of forage yield potential and nutrient components, which can guide farmers in appropriate use of common vetch forages.