Journal of Agronomy and Field Innovations

Production of soybean (Glycine max (L.) Merr.) has increasingly faced difficulties from erratic rains and competing freshwater needs, indicating the need for irrigation management that is accurate and spatially relevant for sustainable intensification. Platforms of unmanned aerial vehicles (UAV) fitted with buildings of thermal infrared and multispectral sensors have become common in defining the variability of the crop water conditions within fields by spatial and temporal accuracy unattainable by satellite or terrestrial solutions. The study summarizes peer-reviewed findings on the possibility of mapping water stress with the help of UAVs and integrating it into precision irrigation scheduling programs in relation to soybean and similar row crops. The principles of thermal imaging are based on the relationship between water stress indications like stomatal opening, reduction of transpiratorial cooling and increase in the air temperature above the canopy. This approach uses a geographic information system (GIS) to create irrigation management zones which leads to improved accuracy of water-status classification when compared to the use of the same sensor only. The use of GIS provides information for the implementation of variable-rate irrigation (VRI) prescriptions which help to reduce the volume of water used while providing similar yield of crops and level of water-use efficiency (WUE). The previously reported improvements depend on the timing of the flights concerning the main phenological stages of soybeans and moisture levels, atmospheric corrections, the use of soil and topographic features in the process of distinguishing zones. The limitations include high cost and sophisticated technology of thermal sensors, lack of common CWSI standards for different cultivars and places, and also low popularity of VRI technology among farmers. Therefore, we come to the conclusion that the use of thermal multispectral fusion via GIS-based software for decision making has great potential in the development of water-efficient approaches to soybean cultivation and requires further investigations to achieve desired results.