Rendimento da cana, terceira folha, sob diferentes níveis de irrigação nos tabuleiros costeiros da Paraíba.

Abstract

In arid and semi-arid áreas, like in the Brazilian Northeast region, where the natural phenomenon of drought usually happens, the use of the irrigation is one of the few options when no the only one, to assure the maintainable agricultural production, mainly if associated to the practice of manuring. With the objective of studying the behavior of the sugarcane third leaf (Saccharum officinarium L., variety SP 791011), under different irrigation leveis and two leveis of manuring, an experiment was installed in the Capim farm of the Miriri distillery, in the municipality of Capim, Paraíba state. The experiment was accomplished through a factorial analysis of the type 2x4 (two leveis of manuring, N0 and Ni and four irrigation leveis, Wo, Wi, W2 and W3) with three replications, totaling 24 different combinations. The leveis of the manuring factor were No = 72 kg ha"1 (28 kg ha"1 of nitrogen and 44 kg ha" of potassium) and Ni = 276 kg ha"1 (112 kg ha"1 of nitrogen and 164 kg ha"1 of potassium). The manuring was applied in a single time. The leveis of the irrigation factor were WQ = 0; Wi = 152; W2 = 290 and W3 = 393 mm. The water application was made through a center pivot irrigation system, in a 12 days frequency, and the evapotranspiration calculation was based on the A class tank, subtracting the effective precipitation. The total amounts of applied water (irrigation plus effective precipitation) were Wo = 275; Wi = 927; W2 = 1.065 and W3 = 1.168 mm. Among the growth parameters studied, the number of stems, the diameter of stems and the internode number and none of the technological parameters were not influenced by the analyzed treatments. The maximum number of stems per hectare was 94.630 (given by the treatment W3 = 1.168 mm and Ni = 276 kg ha"1), which was superior to the ideal minimum limit of 90.000 stems ha"1, presented by the literature in order to obtain maximum productivities. The production of stems and the productivity of sugar and of alcohol were influenced signifícantly by the manuring and irrigation factors, but not signifícantly by the interaction manuring versus irrigation. The mean production of stems obtained in the experiment was of 82,66 t ha"1, the smallest of 68,441 ha'1 (given by the treatment Wo = 775 mm and Ni = 276 kg ha"1) and the largest of 103,091 ha"1 (given by the treatment W3 = 1.168 mm and Ni = 276 kg ha"1). The mean production of gross sugar was of 12,29 t ha"1, the smallest of 9,68 t ha"1 (given by the treatment Wo = 775 mm and No = 72 kg ha"1) and the largest of 15,29 t ha'1 (given by the treatment W3 = 1.168 mm and Ni = 276 kg ha"1). The mean production of gross alcohol was of 8,74 m ha"1, the smallest of 6,89 m3 ha"1 (given by the treatment Wo = 775 mm and No = 72 kg ha"1) and the largest of 10,88 m3 ha"1 (given by the treatment W3 =1.168 mm and NI = 276 kg ha"1). There was increment in the mean production of stems and in the productivity of sugar and of alcohol, with the increase of the irrigation levei in the treatment with larger amount of manuring.