Remote Sensing to Monitor Regulated Deficit Irrigation Effects in Soybean

Remote sensing has already proved to be of great importance to agriculture and irrigation monitoring, allowing the acquisition of a wide array of data over large areas through a variety of sensors and platforms. Regulated Deficit Irrigation (RDI) explores the actual water needs of the plants, aiming at improving irrigation efficiency and reducing water usage. In this work multispectral data acquired through satellite and tethered balloon are compared to measurements made by in-situ sensors. This allows to validate the effectiveness of remote sensing data in this scenario and assess their accuracy and sensitivity to detect crop water stress. The study is conducted over two fields in northern and central Italy, each measuring 160 × 40 meters. The fields are subdivided into four plots, two of which receive full irrigation, while two are subjected to RDI, receiving 70% of the Crop Water Requirement. The fields are monitored during the whole growing season through in-situ sensors and satellite observations in the visible and Near-Infrared wavelengths. The satellite data are provided by the PlanetScope constellation, which offers a spatial resolution of three meters and daily revisit time. Some acquisition campaigns with a tethered balloon are also performed in different growing phases of the crops, allowing to evaluate the evolution of the plants' response at different times of the day. Some of the most widely used vegetation indices are calculated (NDVI, GNDVI, ENDVI, NDRE) as well as the Leaf Area Index, and their values are correlated to different in-situ measurements (precipitation and irrigation levels, crop coefficient, physiological parameters of the plants). Results from the 2022 and 2023 growing seasons are presented. This work could represent a step towards an irrigation scheduling tailored on the actual needs of the plants, rather than relying on predefined timetables, leading to reducing water waste.