Agroindustrial yield of sugarcane grown under different levels of water replacement and nitrogen fertilization

The sugar and alcohol sector has invested heavily in technologies to increase the productivity of sugarcane and consequently the gross income of sugar and alcohol; among these practices irrigation and fertilization stands out. The objective of this study is to evaluate the agro industrial and sugarcane yield (plant cane and first ratoon cycle) grown in the Sudoeste Goiano, Brazil, as affected by water replacement and nitrogen (N) rates; and to evaluate the residual effect from N rates on sugarcane ratoon grown under water replacement levels. The study was carried out with pots filled with a mixture of 120 kg of Oxisol (Rhodic Hapludox) and cattle manure, in a proportion of 3:1 v/v, respectively. A completely randomized design was used, 3x4, with three repetitions, analyzed in split plots. The treatments were combinations of three levels of replacement water (75, 50 and 25% of available water) and four N rates (0, 60, 120 and 180 kg ha-1, equivalent to pots), which were also the same doses for the treatment residual N rate. In both cycles, at harvesting the stem yield and the total recoverable sugar (TRS) were determined for calculation of gross income of sugar and alcohol. The plant cane was not affected significantly by any of the factors evaluated. Interactions between the residual N doses and water replacements influenced the TRS and the gross income of sugar and alcohol in ratoon cane, proving that the N applied on a cycle can be leveraged by another; the stem productivity was affected only by water replacements.   Key words: Residual nitrogen, sugar yield, alcohol yield, irrigation, stem productivity.