On the dependence of salt tolerance of beans (Phaseolus vulgaris L.) on soil water matric potentials

Summary

Bean plants (Kora cv) were grown in potted soil artificially salinized by adding NaCl and CaCl₂ to the irrigation water to obtain an electrical conductivity of the soil saturation extract (EC_e) thirty days after emergence of 0.1, 0.3, 0.5 and 0.7 S/m at 25°C and a sodium adsorption ratio (SAR) of 4 (mmol/l)². Thereafter, plants were irrigated when soil water matric potential (Ψ_M) was in the range of −20 to −30 kPa (wet treatment) and when Ψ_M was in the range of −40 to −60 kPa (dry treatment).

Transpiration rates (Tr) and leaf extension rates (LER) per plant or per unit of leaf area were decreased by increasing soil salinity and by decreasing soil moisture. However, a given decrement of Ψ_M produced a considerable larger decrement in Tr of LER than an equivalent decrement of soil water osmotic potential (Ψ₀). Absolute yields of green pods under wet treatments were from twice to one and a half time as large under the wet than under the dry treatment at equivalent values of Ψ₀. Relative yields were reduced by 25% when EC_e were about 0.5 S/m and 0.7 S/m in the dry and wet treatment respectively. Salt tolerance data of crops may not have a quantitative interest when soil irrigation regimes under which they were obtained are not specified.