TEMPORAL BEHAVIOR OF NDVI MEASURED WITH AN ACTIVE OPTICAL SENSOR FOR DIFFERENT VARIETIES OF SUGARCANE COMPORTAMENTO TEMPORAL DO NDVI MENSURADO COM SENSOR ÓPTICO

Active optical sensors are a new approach for site specific nitrogen management on real time and they have been successfully used on grain crops. This work consisted in evaluating the behavior of the Normalized Difference Vegetation Index (NDVI) using a commercial active optical sensor on 28 sugarcane varieties, as well as analyzing the temporal behavior of this index for each variety throughout the initial 150 days of their productive cycle. The NDVI data was collected with 90, 120 and 150 days after planting (DAP). A descriptive statistical analysis of the data was performed and a Tukey test was applied to contrast the NDVI means. Results indicated that the varieties interfere in the NDVI readings and, in general, the readings with 90 DAP were different from those with 120 and 150 DAP, tending to stabilize along time for each variety