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Identifying annual forage legumes suitable for summer cultivation can be a solution for forage production. Annual summer grain legumes such as cowpea, mung bean, and guar also have good potential for forage production. These summer crops would have different potential of forage yield, especially in drought conditions. Therefore, the objective of this study was to evaluate the quantitative and qualitative forage traits of these three types of summer legumes, including cowpea (Mashhad cultivar), mung bean (Parto cultivar), and guar (local cultivar of Sistan) under drought stress conditions. Methods: A split-plot experiment in a randomized complete-block design with three replications was conducted at the Seed and Plant Research Improvement Institute (SPII), Karaj, Iran for two years in 2019–2020. The study included three irrigation treatments (30, 50, and 70% soil-moisture depletion) as the main plots and the three legume species as subplots. The highest mean fresh forage yield was obtained for cowpea and mung bean (22.29 and 20.39 t ha−1, respectively), while 9.37 t ha−1 was obtained for guar, although dry forage-yield difference between cowpea and mung bean was not significant (5.03 and 4.71 t ha−1, respectively). In addition, dry forage-yield difference between 30 and 50% soil-moisture depletion was not significant (4.58 and 3.77 t ha−1, respectively). The highest percent of crude protein was observed at normal irrigation for mung bean (16.97%). Furthermore, the highest levels of insoluble fiber in neutral detergent (NDF) and metabolizable energy (30.90 and 2.30, respectively) were observed for mung bean at severe stress. The highest mean forage yield was obtained for cowpea and mung bean, and irrigation after 50% soil-moisture depletion in the three legume species can be recommended. |
