Efeitos de diferentes níveis de adubação, sobre a produção da terceira folha de cana irrigada nos tabuleiros costeiros da Paraíba.

Abstract

The sugarcane is fundamental for production of alcohol and sugar. In the traditional areas, mainly in the areas of expansion of the sugarcane crop in Brazil, the manuring constitutes an essential practice for the reach of higher productivities. Thus, the appropriate use of the fertilizers becomes indispensable for obtaining profitable productions. Therefore, considering the perspective in the increase of the productivity, the present research had the objective of identifying the effect of different manuring levels on the production o f the third leaf of irrigated sugarcane (variety SP 79 1011) in the Paraiba state coastal lands. Specifically, the following growth parameters were studied: number of stems, length, diameter, number of internodes per stem, weight of stems; and also the following technological parameters: soluble solids (°BRIX), percentage of sucrose (POL), purity o f the broth, industrial fiber of the sugarcane, amount of sugar contained in the stem (PCC), production of stems and gross yield of sugar and alcohol. The research was developed in Capim I I farm owned by the Miriri, distillery in the municipality of Capim, in Paraiba state. The experimental was accomplished through a factorial scheme of 2 x 4 (with, WI, and without, WO, irrigation and four levels of manuring, NO, N I , N2 and N3), with three replications. The water depth, applied in intervals of irrigation of 12 days, was 27,5 mm. The total water depths applied through the season were 775 mm (WO), only from rainfall, that is, in the non-irrigated area, and 1065 mm (WI), from irrigation and rainfall in the irrigated area. The manurings were composed of the elements N and K 2 0 in amounts based in the levels recommended by the consultants of the Miriri distillery, which were: NO = 72 kg ha"1 (level used in the farm, 28 kg ha"1 of nitrogen and 44 kg ha"1 of potassium); N I = 174 kg ha"1 (68 kg ha"1 of nitrogen and 106 kg ha"1 of potassium); N2 = 276 kg ha"1 (112 kg ha"1 of nitrogen and 164 kg ha"1 of potassium); and N3 = 378 kg ha"1 (156 kg ha'1 of nitrogen and 222 kg ha"1 of potassium). The crop when submitted to irrigation presented better yield in all growth parameters, when compared to the irrigation absence. The maximum number of stems per hectare was 91,944 (given by the treatment WI = 1065 mm and N3 = 378 kg ha"1), which was superior to the ideal minimum limit of 90,000 stems ha"1 registered by the literature. The production of stems was influenced significantly by the irrigation factor, but the manuring and the interaction among the factors had non-significant effect. The mean production of stems obtained in the experiment was 80.491 ha"1, the smallest 68.441 ha"1 (W0 = 775 mm and N2 = 276 kg ha"1) and the largest 97.29 t ha"1 (WI = 1065 mm and N3 = 378 kg ha"1). The mean production of gross sugar was 11.82 t ha"1, the smallest 9.68 t ha"1 (W0 = 775 mm and NO - 72 kg ha" l ) and the largest 14.71 t ha"1 (WI = 1065 mm and N3 = 378 kg ha"1); while the mean production of gross alcohol was 8.41 m3 ha"1, the smallest 6.91 m3 ha"1 (W0 = 775 mm and NO - 72 kg ha"1) and the largest 10.46 m3 ha"1 (WI = 1065 mm and N3 = 378 kg ha"1). However, the technological parameters of the sugarcane (POL, fiber and PCC) responded significantly only to the irrigation treatment, while the °Brix and purity did not respond to none of the factors.