Produtividade e qualidade da cana-de-açúcar sob níveis de adubação nitrogenada e lâminas de irrigação.

Abstract

Knowledge of adequate water management in the region suffering from rainfall irregularity, as well as the level of nitrogen that will meet the nutritional requirements of sugarcane, are fundamental factors to obtain better yields in terms of productivity and technological quality. Thus, the objective of this work was to evaluate the productivity and quality of sugarcane under nitrogen fertilization levels and irrigation slides, under the conditions of the Northern Zone of the State of Pernambuco. The experiment was carried out in two consecutive years, in the cycles of cane plant and ratoon regrowth, under field conditions at Fazenda Olho D'Água in the municipality of Itambé - PE. The treatments consisted of two sugarcane varieties (RB92579 and RB002754), four irrigation depth (L1=12; L2=45; L3=100 and L4=125% of Evapotranspiration of The Crop - ETc, for the cane plant cycle) and L1=10; L2=40; L3=100 end L4=125% of ETc ) for cane regrowth and four nitrogen fertilization levels (N1 = 0, N2 = 50, N3 = 100 and N4 = 200 kg ha-1 of N). The data were submitted to analysis of variance through the R program, and when significant for quantitative factors the regression for the Tukey test qualitative factors at the 5% level was performed. The sugarcane irrigated with the largest depths in the cycles of cane plant and regrowth promoted higher growth in plant height, stem diameter, number of tillers and produced an average of 45.0 t ha- 1. The recoverable total sugars (ATR), sugar yield (TPH) fiber content and purity is positively related to the increase of the irrigation depth in the cane plant and regrowth, and the fiber content has a negative relation with the levels of independent nitrogen of the variety used. The RB002754 variety was superior to RB92579 in the biometric parameters, TCH and water productivity in the plant sugarcane cycle, however the RB92579 obtained better performance in the regrowth cycle for TCH, ATR and purity. In the plant cane cycle there was greater export and requirement of macronutrients for RB92579, and for cane regrowth the highest averages were of RB002754. The nutritional requirement to produce a ton of stalk per hectare and the export of nutrients showed a higher requirement for macronutrients in cane regrowth, except for potassium. The RB92579 variety was considered to be more efficient in the use of macronutrients due to their low requirement and are recommended for soil lower natural fertility. The yield of water based on stalk and ATR was inversely related to the increase in irrigation depth independent of the studied variety RB002754 or RB92579 for the cane and plant cycle. Nitrogen productivity decreases markedly with increasing levels of N, from 0 kg of N ha-1 on the cane and plant cycle.