RESPONSE OF COTTON PRODUCTIVITY SUBMITTED TO DIFFERENT DOSES OF NITROGEN AND EFFICIENCY OF THE OPTICAL SENSOR TO ESTIMATE YIELD POTENTIAL - DOI: 10.13083/1414-3984/reveng.v23n1p57-64

Abstract

The development of the cotton crop is directly influenced by nitrogen nutrition, which is dependent on mineral fertilization. However, the management of nitrogen by this culture is complex, since large doses can also cause negative effects on crop yield. In this context, fine-tuning the dosage of N fertilizer, according to the crop demands, is essential to obtain high yields. This study sought to: I - establish the response curve of cotton yield to N fertilization, II – evaluate the capability of the optical sensor to estimate yield potential. The experiment was conducted in the agricultural year 2012/13 in an Oxisoil in the western region of the state of Bahia, in three areas with tropical climate, annual rainfall of 1600 mm yr-1 and a mean annual temperature of around 21 oC. The experiment was setup in a randomized block design with seven treatments and three replications. The treatments consisted of the following N doses: 0, 45, 90, 130, 150,180 and 220 kg ha - 1 applied at 43 days after sowing (DAS) in area 1 and 32 DAS in areas 2 and 3. The vegetation index (VI) readings were taken at three different times, corresponding to 63, 75 and 97 DAS in area 1 and 45, 57 and 80 DAS in areas 2 and 3, using the optical sensor N-Sensor ALS ® (YARA). For the different areas and VI readings the cotton yield was determined. The productivity of the cotton crop showed a quadratic fit with N doses studied in three experiments and the rates which achieved maximum economic efficiency were 164, 139 and 167 kg ha-1 of N for areas 1, 2 and 3, respectively.