Forage yield and nutritive value of summer legumes as affected by row spacing and harvest timing

Winter wheat (Triticum aestivum L.) is an essential, high-quality forage used for grazing stocker cattle from fall to spring in the US Southern Great Plains (SGP). However, the lack of nutritious forages during summers limits grazing by stocker cattle. To fill this quality gap, a short season species capable of producing significant yield and quality of forage is necessary. A two-year experiment was conducted to evaluate the performance of three legumes: tepary bean (Phaseolus acutifolius A. Gray), mothbean [Vigna aconitifolia (Jacq.) Marechal], and soybean [Glycine max (L.) Merr.] as a control, at different harvest dates, in response to different row spacing (38 ​cm and 76 ​cm) and moisture levels (rainfed and irrigated). Results showed forage yield by all legumes planted at 38 ​cm spacing (4.5 and 3.9 ​Mg ​ha⁻¹) was higher than at 76 ​cm spacing (3.4 and 2.4 ​Mg ​ha⁻¹) in 2018 and 2019. Soybean was the most productive while mothbean had the highest relative feed value (RFV) in both 2018 and 2019 (160 and 118, respectively). Although soybean produced more forage, mothbean and tepary bean provided high quality forage in terms of neutral detergent fiber (NDF), acid detergent fiber (ADF), and in-vitro true digestibility (IVTD). The results indicate that no single legume species stands out as the unequivocal leader in delivering both high-quality and abundant forage. Consequently, the choice of which species to utilize should be tailored to the specific forage requirements and management goals. Future research should explore mothbean genotypes to identify cultivars with greater yield potential and develop agronomic practices that effectively utilize those cultivars.