Crescimento da cana-de-açúcar sob irrigação e parcelamento da adubação nitrogenada.

Abstract

The water and nutrients are factors that make influence in the quantitative and qualitative production besides the growth of any culture. Aiming to study the effect of the splitting of nitrogen fertilization and irrigation depth water in sugar cane plant on its growth, so it was developed an experiment at the Destilaria Miriri S/A, Capim II Farm, in the period from October/2008 to September/2009, in a dystrophic Yellow Red Clay Soil. The tested irrigation depth water were: dryland, 25 % of ETc (128.00 mm), 50 % of ETc (191.05 mm), 75 % of ETc (379.31 mm), 100 % of ETc (680.08 mm) and 125 % of ETc (913.95 mm) with the respective effective rain 943.50, 925.60, 876.42, 705.86, 567.24 and 394.67 mm; the nitrogen fertilization was fixed in 600 kg ha"' of Ammonium Sulphate, applied in four splitting 'P': Pj (600 kg ha"1 of Ammonium Sulphate on the 4t h month after the planting), P2 (300 kg ha"1 of Ammonium Sulphate on the 4t h and 5t h month after the planting, respectively), P3 (200 kg ha"1 of Ammonium Sulphate in the 4t h , 5t h and 6l h month after the planting, respectively) and P4 (150 kg ha"1 of Ammonium Sulphate in the 4t h , 5t h, 6t h and 7t h month after the planting, respectively), composing a 6 x 4 factorial scheme, totalizing 24 treatments with 3 replications, the experimental design was in randomized blocks, and analyzed jointly. The used variety was the RB 92 579. The irrigation system was the fixed pivot, with irrigation turn defined in function of the hydric and physical soil analysis, to each seven days using 100% of the soil water, varying the speed of the equipment by irrigation sector, to the application of the corresponding water depths to the treatments. The ETo was defined by Penmann & Monteith equation and the ETc was determined in function of the plant age and its respective Kc. The growth variables (tillers, stalk height, leaf area, leaf area index, biomass of leaves and stems) were valued monthly, since 60 to 330 days after planting. On 90 days after the planting the regression analysis was carried out, wrapping only the ETc replacement factor, because of the nitrogen fertilization started on 120 days after the planting; from this date the statistical analysis included two factors. The sugar cane tillers were decreasing with time, independent of the irrigation depth. The highest plants stalk occurred with the application of 100% of ETc; on 240, 300 and 330 days after the planting, this variable was influenced by the splitting of the nitrogen fertilization. The sugar cane leaf area irrigated with 125% of ETc was superior in 19.75%, regarding the treatment of 100% of ETc. The highest leaf area index (5.45) was in the culture irrigated with 125% of ETc and this same blade was obtained also the maximum leaf biomass accumulation with 76.78 grammes, around, to 270.91 days after the planting. The highest stem biomass accumulation was obtained in the sugarcane irrigated with 100% of ETc.