Foliar Nitrogen Estimation with Artificial Intelligence and Technological Tools: State of the Art and Future Challenges

Nitrogen plays a fundamental role in plant growth, but its high application has significant negative impacts for the farmers and the environment. This nutrient is often provided in excess to prevent plant growth limitations when it ought to be administered in the exact quantities because many farmers do not have access to technology or affordable soil and plant chemical analyses. Precision agriculture through monitoring of crop nutrition may be possible with quantitative, non-destructive methods and technological tools that allow farmers to conduct a rapid and representative verification of their fertilizer applications. In this sense, we carried out a systematic review and bibliometric analysis of recent scientific research to answer the questions: 1) Can artificial intelligence-based, nondestructive analysis of plant nutrition provide relevant information for decision-making in agricultural systems?, 2) Have recent studies reached the stage of developing technological tools to be applied in agricultural systems and field conditions?, and 3) What is the way forward to achieve popularization of the application and development of technological tools in agricultural systems? We found that non-destructive analyses of foliar nutrition need to provide more supportive information for decision-making given the challenge of interpreting and replicating results in agricultural systems operating under uncontrolled conditions, such as field conditions. To address this issue, we propose developing accessible technological tools, such as mobile applications, tailored to farmers' needs. However, most studies had not yet considered developing a technological tool as part of their objectives. Therefore, it is critical to develop accessible and affordable technologies and monitoring systems that approach precision agriculture since the conservation and sustainable management of natural resources demands translating scientific knowledge into supporting tools that reach farmers and decision-makers worldwide. The way forward is innovation through technological developments that enhance current agricultural systems.