Nutrição e produção de bananeira ‘pacovan’ fertirrigada com nitrogênio e potássio utilizando água superficial poluída.

Abstract

In the Brazilian Northeast, fruit growing is based on unique climatic conditions, combining the high luminosity indexes with high relative humidity and low air humidity. In this scenario, banana cultivated is seen as one of the most profitable and promising agricultural activities, Especially in the irrigated fruit farms. In this context, was evaluated the influence of fertirrigation with different doses of nitrogen and potassium through the low-quality water of the Bodocongó River, on the productive and nutritional constituents in leaves and fruits, in two productive cycles, of the 'Pacovan' banana. The studies were conducted at Ponta da Serra farms, on the margins of the Bodocongó river, where two factors were tested. Nitrogen (0, 100, 200 and 300 kg ha-1 year-1 in the form of ammonium sulfate) and Potassium (0, 150, 300 and 450 kg ha-1 year-1 in the form of potassium chloride), in the block design with treatments arranged in a 4 x 4 factorial scheme, with three replications. During the studies, the monitoring of the chemical quality of the water used in the irrigation of the banana tree was carried out through periodic evaluations of the parameters: pH; CEa; N; P-orto; K; Ca; Mg; Na; HCO3; CO3; Cl e RAS. The diagnoses of the nutritional status of the crop, elaborated from the Integrated System of Diagnosis and Recommendation - DRIS, were investigated in two productive cycles. In this context, and among the obtained results, it is perceived that, irrigation with water from the Bodocongó River should be practiced with caution, since high levels of Na+, CO3 --, HCO3 - and Cl- are transported to the soil by irrigations, which makes it limiting to the continued use in irrigated productive systems, because it has salinity ranging from medium to very high, sodicity oscillating between low and medium and moderate toxicity to plants. The contribution of essential nutrients from the water of the Bodocongó River, mainly N and K, allowed to reduce the amount of nitrogen and potassium fertilizers, without prejudice to the nutritional status of the crop. In which the nutritional balance of N and K in the second cycle and N and Fe in the third cycle were verified in fertigated plants with 19 kg of K ha-1 and 15 kg of N ha-1. These doses produced productivities of 14.2 t ha-1 in the second cycle and 24.3 t ha-1 in the third cycle; Being harvested bunches with only 6.0 kg less, containing fruits only 15.3 g lighter, 2,5 cm smaller and 0,5 cm less thick than those found in the maximum doses of N and K defined by the statistical models. Likewise, it is important to mention that the levels of K and Mn found in fruits harvested in the third cycle exceeded the maximum nutritional limits for daily intake defined by the National Academy of Sciences and, therefore, may present restrictions for consumption.