ALTERAÇÕES FISIOLÓGICAS EM FEIJÃO-CAUPI IRRIGADO COM ÁGUA SALINA E ADUBAÇÃO NITROGENADA PHYSIOLOGICAL CHANGES IN COWPEA UNDER SALINE WATER AND NITROGEN FERTILIZATION

Excess salts in the soil cause physiological damage in vegetables such as, reduction of photosynthesis, transpiration and stomatal conductance, compromising crop development. The objective was to study the physiological parameters in cowpea cv. BRS Pajeu under different levels of salinity of irrigation water and doses of nitrogen. The experiment was conducted in drainage lysimeters in the period June to September 2013 in a greenhouse. An experimental design of randomized blocks was used in factorial (5 x 5), five levels of electrical conductivity of irrigation water - ECw (0.9, 1.8, 2.7, 3.6 and 4, 5 dS m -1 ) and five doses of nitrogen fertilization (70, 100, 130, 160 and 190% of nitrogen recommended for pot experiment). The study evaluated photosynthesis (A), transpiration (E), stomatal conductance (gs), internal concentration of CO2 (Ci), instantaneous efficiency of carboxylation (EICI) and intrinsic water use efficiency (EUA). Nitrogen fertilization behaved similarly in different levels of salinity of irrigation water. Except internal concentration of CO2 gas exchange decreased linearly with increasing electrical conductivity of irrigation water.