Growth Performance of Beach Bean (Canavalia maritima Thouars) on Three Soil Types Irrigated with Saline Water

Beach bean (Canavalia maritima Thouars) is a wild legume distributed exclusively on coastal sand dunes, with potential of being domesticated for its nutritional attributes and utility in agriculture. A pot experiment was conducted to investigate its seedling performance under sand, loam and clay soils irrigated with 0 (control), 25, 50, 100, 150 and 200 mM NaCl saline water. In sand, mortality occurred only at 200 mM with 70% survival. Survival reduced at 150 and 200 mM to 80.48 and 56.34% respectively in loam. In clay, 61.8 and 43.14% plants survived at 100 and 150 mM while no plants survived at 200 mM. Growth parameters including number of nodes, internode length, plant height, number of leaves and branches, root length, root number and relative growth rate increased significantly (P=0.05) at 25-150 and 25-100 mM NaCl in sand and loam respectively, but decreased significantly (P=0.05) at higher concentrations, compared to the control. Fresh and dry mass of plant parts and total biomass in sand and loam followed similar trends with the growth parameters. All the variables decreased significantly (P=0.05) in clay with increasing concentration of saline water. Stem girth increased while leaf area and leaf total chlorophyll decreased significantly (P=0.05) in all the soil types irrigated with saline water. Root/shoot ratio also increased but was significant (P=0.05) only in sand. Salinity induced leaf and stem succulence, led to a significant (P=0.05) reduction in pre-dawn xylem water potential and caused accumulation of Na+ and Cl- in the plant tissues. Canavalia maritima can be propagated in sand and loam soils, with optimal growth when irrigated with saline water containing 25-150 mM and 25-100mM NaCl respectively.