Field Performance and Nodulation of Yardlong Bean in the Humid Tropics

Abstract

Yardlong bean [Vigna unguiculata (L.) Walp. subsp. sesquipedalis] is a popular vegetable grown throughout the tropical Far East, including Guam. There is little information on growth response of yardlong beans and nodulation by indigenous bradyrhizobia colonized in agricultural soil regimes of Guam. Five cultivars of yardlong bean were evaluated in a 2-year study for their field performance and nodulation with indigenous bradyrhizobia on a Pulantat clay soil (Barrigada), an Akina silty clay soil (Ija), and a Guam cobbly clay loam soil (Yigo) on Guam. The 1996 experiment was conducted during the dry season (12 Feb.–10 May) and the 1997 trial in wetter months (28 Apr.–25 July). The study indicated that season, location, and cultivar affected pod yield. The cv. Green Pod Kaohsiung grown in Barrigada during the dry season had the highest pod yield. ‘Local Selection’ was one of high yielders in all sites in both seasons. Nodulation was observed at all locations with the least number of nodules found at Yigo with a calcareous alkaline soil. ‘Local Selection’ had the most nodules at Ija with an acidic silty clay soil. There was no correlation between the number of nodules found in roots and pod yield. The study indicated that yield potential of yardlong bean would be improved by selection of planting season, location, and cultivar.