Methods have been proposed seeking to improve the application of nitrogen (N) simultaneously with yield increase and environmental protection, reducing the nitrate concentration in the soil and in the water. One of these methods, precision agriculture consists of the site-specific application of the agricultural inputs as a function of the local need. In this context, the measurement of the spectral leaf reflectance shows itseif as a promising method for the instantaneous remote sensing of deficiency of N in corn through the calculations of vegetation indexes. However, the characteristics of the interaction of the plants with the solar radiation are not well known. This work evaluated the behavior of the vegetation indexes in relation to the hour of the day and the applied nitrogen rate. Six different indexes were studied: relationship near-infrared/red (NIR/red), relationship near-infrared/green (NIR/green), normalized difference vegetation index (NDVI), green normalized difference vegetation index (GNDVI), soil adjusted vegetation index (SAVI) and optimized soil adjusted vegetation index (OSAVI). When only the data collected around the half solar day weve analized, the indexes that presented the lowest dispersion results were NDVI and OSAVI. For data collected during the whole day the indexes that presented better explanation of the variability were SAVI and OSAVI.
precision agriculture; reflectance; remote sensing; Zea mays L
