Rendimento agroindustrial da cana-de-açúcar sob suplementação hídrica e parcelamento de nitrogênio.

Abstract

and physiological processes in general, reflecting in the quantitative and qualitative production of any crop. In sugar cane, there are few studies with this focus, especially in Northeast of Brazil. In order to study the effects of splitting of nitrogen fertilization and irrigation on agroindustrial yield of sugar cane, variety RB 92-579, an experiment was carried out at Miriri Distillery SA, in Capim city - PB from October/2008 to October/2009 (plant-cane) and from October/2010 to October/2011 (ratoon-cane) in a Argisoil Red-Yellow dystrophic. The treatmente consisted by combination of leveis of evapotranspiration replacement (0, 25, 50, 75, 100 and 125% ETc) and four fractions of nitrogen (4, 5, 6 and 7 months after planting), being applied a fixed amount of 600 kg ha*1 of ammonium sulfate. An irrigation system of fixed pivot was used. Growth variables (height, leaf area, leaf area index, tiller number, leaf diy matter, dry matter of stalks and total dry matter) were collected monthly from 60 to 330 days after planting, in the first cycle, and from 60 to 300 days after bud break in the second cycle, and at the harvest (360 days after planting) of the sugar cane was obtained the productivity and water use efficiency, proceeding repeated in the second cycle. It was also determined harvest index in both cycles. The stalks of the first and second cycle were subjected to technological analysis in the laboratory at Miriri Distillery S.A. The data of splitting were submitted to analysis of variance by F test. When had significance it was performed polynomial regression analysis for quantitative factor and for qualitative factor was performed Tukey test (p < 0.05) for comparison of means. Until the fourth month after planting was held statistical analysis with a single factor, irrigation depth water, and after whereas that nitrogen fertilization was carried at 120 days after planting, me analysis of the study consisted of two factors. Tillering of sugar cane is not influenced by irrigation in plant-cane but in ratoon-cane, with increasing of irrigation increased the number of tállers. With 125% of ETc in the plant-cane was obtained maximum values of leaf area, leaf area index and leaf dry matter, the next harvest these higher values were found with 100% ETc; the stalk dry matter was higher in plant-cane irrigated with 100% of ETc and 125% of ETc in ratoon-cane. Irrigation influences in the stalk productivity and water use efficiency in two cycles, and the yield of sugar only in the second cycle. Splitting of nitrogen provides effect in the stalk productivity on the plant-cane and on the ratoon-cane this effect is larger irrigation depth water. Among ali technological indexes only the °Brix, the PCC and pol (in the first cycle) and °Brix, pol, purity, fiber, PCC and ATR (in the second cycle) are altered by irrigation. The industrial quality of sugar cane was not modified by splitting nitrogen fertilization.