UAV-thermal imaging: A technological breakthrough for monitoring and quantifying crop abiotic stress to help sustain productivity on sodic soils – A case review on wheat

Abstract Demand for food and other agricultural products is projected to increase by 50% globally by 2050. This increasing food demand places growing pressure on agricultural production at a time where there is little scope to expand agricultural lands. In addition, other constraining factors, such as climatic and soil constraints negatively impact agricultural productivity at global scale. To help ensure future food security, we must improve soil-crop management practices to achieve optimum productivity. One major area where productivity could be improved is for crops grown on dispersive sodic soils, which currently affect over 581 million ha worldwide. One strategy is to identify crops and/or cultivars that are more stress tolerant and productive on sodic soil and can improve agricultural productivity. However, limited work has been done to identify tolerant varieties and there is a pressing need for innovative and improved solutions to identify stress tolerance. In recent years, unmanned aerial vehicle (UAV)-based thermal imaging has been widely used in precision agriculture for detecting crop diseases and stress, and this technique has significant potential to also assess crop performance on sodic soils. In this review, we present the current understanding of how thermal imaging techniques can provide a viable technological solution to monitor crop temperature and quantify abiotic stress, which is one of the major causes for yield loss of the major rain-fed field crops, particularly wheat. To the best of our knowledge, no such detailed review has been published. Being able to identify plant stress is a primary requirement to identify more or less tolerant species or cultivars grown on sodic soil under rain-fed conditions. The aim of this review is to provide a clear and concise summary of the impacts of abiotic stress on crops and the use of UAV-thermal imaging, including sensors and calibration, data processing, advantages, and limitations in crop phenotyping, and particularly quantifying abiotic stress to help sustain productivity in sodic soil environments.