Alteration of the physiologic characteristics in banana under fertirrigation conditions

Fertilizer application through the irrigation system, has become an important way to supply nutrients to fruit trees. However, it is necessary to study its effects on the banana tree physiology, in order to improve fertilizer use efficiency. The objective of this study was to evaluate doses of nitrogen and potassium through irrigation water, on the physiological characteristics of the banana tree, cv. 'Prata-Ana', in the coastal tablelands of Sergipe State. The experiment was established in the field, using a 4(2) factorial with four randomized blocks, at the Sergipe Federal University Experimental Station. Two factors were tested: nitrogen (0; 250; 500 and 750, in kg ha(-1) of N, as urea) and potassium (0; 290; 580 and 870, in kg ha(-1) of K2O, as potassium chloride). Rate of net CO2 assimilation, transpiration, stomatal conductance, internal leaf CO2 concentration, water use efficiency and carboxylation efficiency were determined. The stomatal conductance was reduced in the fertilization with 700kg ha(-1) of N and absence of K, affecting the gas exchanges and, consequently, the photosynthesis. In situations of higher potassium readiness, the banana trees need smaller amounts of nitrogen in order to maintain the efficiency in the water use, as consequence of the best stomatal adjustment.