Abstract

A study was conducted to determine the optimal level of nitrogen for a better performance of the virgin canes. The vegetal materiel is composed of the variety SP 70-1284. The materiel of laboratory is composed of an electric grinder ("Jeffco" food and fodder cutter grinder, model 265 B, set L 1710), a refractometer (Schmidt+Haensch, HARD-SW model, set 29129) and a polarimeter (Saccharomat Z, set 29305). The test was conducted with the variety SP 70-1284 as an experimental randomized complete block with 9 treatments, with 4 repetitions. The total doses of N of three contributions for the cycle of harvest (35, 70, 105, 140, 175, 210, 245, 280, 0 kg ha 1) correspond to the T1 treatments, T2, T3, T4, T5, T6, T7, T8 and T0. The T0 (14, 79 t s ha-1 ± 1, 03) recorded the weak quantity of sugar. The quantity raised of sugar has been observed on the T8 (16, 83 t s ha-1 ± 1, 09), T5 (16, 84 t s ha-1 ± 1,15) and T7 (16,94 t s ha-1 ± 1,12). The weak rate of the Brix has been revealed on the T2 (22, 05% ± 0, 84). The T4 (23, 15% ± 0, 77), T3 (23, 21% ± 0, 21), T8 (23, 43% ± 0, 62) recorded the strong rates of the Brix. The elevated Pol rate is gotten with the T8 (20, 90% ± 0, 55), the lowest with the T2 (19, 45% ± 0, 80). The weak rate of Wealth Hugo Simplifiée (RHS) is recorded on the T2 (12, 84% ± 0, 55), the T8 (13, 87% ± 0, 45) got the elevated rate. The dose of 280 kg N ha-1 corresponding to T8 appears to be effective and can be used for the profitability of the variety SP 70-1280 to the Agro Industrial Complex of the CST-Banda in Chad.