The influence of N concentration and NO3/NH4 ratio on the growth of lima and snap bean and southern field pea seedlings

Abstract

Lima and snap beans and southern field peas were cultured in a modified Hoagland's solution for 14 days with N supplied as Ca(NO₃)₂ and/or (NH₄)₂SO₄ at three N concentrations and five ratios of NO₃ to NH₄. The ratio of NO₃/NH₄, rather than the N concentrations influenced seedling growth of these vegetable legumes. Maximum seedling growth of lima bean was generally obtained with all combinations of NO₃ and NH₄. A preference for 75% NO₃ and 25% NH₄ was observed for snap bean. Southern field pea growth was reduced only when all of the N was supplied as 100% NH₄. Ammonium toxicity symptoms, lesions and severe wilting, developed with snap bean and southern field pea within 14 days when cultured with 100% NH₄. Lima bean, though reduced in growth, exhibited a tolerance to the 100% NH₄ treatment.