Sensing for sustainable agriculture with focus on developing technologies for monitoring plant stress

Abstract

Global demand for food, water and energy, with climate change and increasing variability in growing conditions, are among the key defining challenges of our time. With the impact on the environment, the onset of global warming, major crop-producing countries reaching their freshwater limit, unpredictable variability in climate, reduced land fertility from drought, erosion and poor management, and the ever-increasing public expectations for more sustainable practices to reduce the use of water and agrochemicals, it has never been more important to achieve efficiency and sustainability in agriculture. The development and deployment of sensing technologies is one of the main steps in achieving sustainability in crop production through precision agriculture. In order to reach our agricultural output goals sustainably, we not only need to make crop production efficient through precision resource management but also reduce yield losses due to stress in plants.

Traditionally, crop health is determined through manual visual inspections based on physiological signatures such as lesions, tumors, wilting, stunted growth, discolorations and cell death. At that stage, the majority of the damage had already occurred, leaving little to no room for treatments. Alternatively, based on prior knowledge and/or rule of thumb, growers may apply agrochemicals like, pesticides, fungicides or bactericides to prevent pest and/or phytopathogenic damages, however, the application is not optimized and often the chemicals are used in excess leading to environmental contamination as well as economic stress. Therefore, identifying stress responses in plants in a timely manner is of critical importance with a direct impact on yield, food security, agricultural economics and the environment.

The progress made towards understanding the defense mechanisms in plants, from the moment of coming in contact with a stressor to expressing physiological measures and effects, has paved the way for developing sensing techniques for crop health management to improve the sustainability of the agroecosystems. Methodologies enabling early and accurate detection of plant stress due to pathogens and pests provide a way for optimal deployment of countermeasures for reducing losses in yield.

This dissertation presents the research and developments in the field of plant health monitoring and electrochemical sensing, where first, an in-depth literature review of the sensing methodologies for monitoring biotic stress in plants is presented which helped identify phytohormone detection-based plant health monitoring as the prime area of interest. Next, novel sensing technologies were developed including salicylic acid (a critical defence-related phytohormone) detection, a portable electrochemical sensing system, and data analysis procedures. Additionally, a novel electrochemical method named multi-set differential pulse voltammetry (DPV) derived from a conventional DPV technique is presented that provides a way for reducing random error in electrochemical sensing without incurring any additional cost in terms of time, energy and/or resources. The developments reported in this dissertation are aimed at progressing the state-of-the-art agricultural, biological and chemical sensing technologies that may help achieve efficiency and sustainability in our practice of agriculture.