Utilization of Multispectral Imagery in Orange Trees Cultivated with Agricultural Gypsum Application in Eastern Amazon

Abstract Remote Sensing enables the acquisition of planting information through the spatial resolution of multispectral images obtained from Remotely Piloted Aircraft (RPA) in situ. This study aimed to evaluate the application of agricultural gypsum in citrus orchards using precision agriculture tools and image-based analysis. Multispectral images were acquired at three flight altitudes (80, 100, and 120 m) to assess their influence on canopy area delineation and the Normalized Difference Vegetation Index (NDVI). The experimental design consisted of five gypsum application rates (0.0, 0.6, 1.2, 1.8, and 2.4 t ha⁻ 1 ) applied to a citrus orchard located in Capitão Poço, Pará, Brazil. The variables analyzed were NDVI – derived from near-infrared and red reflectance bands – and canopy area, extracted from vector polygons of tree crowns. The results showed that the 0.6 t ha⁻ 1 dose yielded the greatest canopy area. Additionally, flights at 80 m altitude provided higher spatial resolution, enabling more precise delineation of citrus canopies. This enhanced detail supports improved vegetation monitoring, emphasizing the advantage of higher spatial resolution in precision agriculture.