A field experiment was carried out in São Paulo State, Brazil, with the objective of investigating the response of 'Nanicão' banana (Musa AAA Cavendish subgroup) to nitrogen and potassium fertilization, under irrigated and non-irrigated conditions, during two crop seasons. A split-plot design was used with irrigation (micro-sprinkler) and no irrigation applied to main plots and a combination of four rates of N (0, 200, 400 and 800 kg N ha-1) and K (0, 300, 600 and 900 kg K2O ha-1) as the sub-plots treatments. The area was managed according to regional recommendations; special attention was paid to disease control and irrigation management. The effects of treatments on life span of leaves were assessed counting leaves at flowering (NFE) and at bunch harvest (NFC), calculating leaf longevity index (IDF=NFC¸NFE´100) and studying N and K leaf contents. Irrigation and K fertilization caused a significant increase in leaf longevity (p<0.05). The NFC with irrigation (7.2) was greater than in non-irrigated plots (3.8). In the first ratoon crop, the K/N ratio that provided greatest leaf longevity was 1.6 for non-irrigated plants (IDFnon-irri=49%) and 1.4 under irrigation (IDFirri=68%). Irrigation and accurate fertilization (avoidance of low K/N ratio) showed to be useful for increasing life span of banana leaves.
banana; Musa spp.; senescence
