Agricultural Sustainability by Monitoring with Affordable Re-usable TouchScreens (Project Agri-SMARTs)

In cutting edge sustainable farming in the UK, large glasshouse farms have irrigation systems that deliver nutrients directly to the plant roots in soilless systems, a form of aquaculture fertigation. This approach to farming is crucial in the UK in the drive to improve sustainability, reduce local environmental impact, reduce greenhouse gases and contribute to UK food and nutrition security. The problem identified is that currently there is no affordable method for in-line measurements of the nutrients being fed to the plants. Affordable integrated sensors that track nutrients are also needed for rapid and accurate tuning at every stage of the growth cycle to drive cost reduction, fertiliser and nutrient use efficiency and optimise yield response and flavour. There is an exciting potential sensing solution in the form of touchscreen technologies. Touchscreen technology is ubiquitous in our everyday lives. The screen on a typical smartphone is covered in a grid of electrodes, and when a finger disrupts the local electric field of these electrodes, the phone interprets the signal. Instead of interpreting a signal from your finger, what if we could get a touchscreen to read nutrients/electrolytes, since these ions also interact with the electric fields? We have shown how a typical touchscreen could be used to identify common ionic contaminants in soil or drinking water by dropping liquid samples on the screen, the first time this has been achieved. The sensitivity of the touchscreen sensor is comparable to typical lab-based equipment, which would make it useful in cost-sensitive or low-resource settings. In this project, we will simplify the sensors further to ensure they are easy affordable to manufacture and easy to tune for different ions of interest. These will be integrated into the site of a partner farm to demonstrate how nutrient tracking can deliver incredible advantages through precision agriculture.

In sustainable farming in the UK, large glasshouse farms have irrigation systems that deliver nutrients directly to the plant roots in soilless systems. Currently, while the initial concentration can be defined, growers need to collect samples of the aqueous nutrient streams across the rest of the system and send samples away for analysis, at great expense and with least a 1-week time delay. This does not allow the nutrient mix to be adjusted to optimise yield response, flavour and to impact CO2 eq. A shift to in-line, instantaneous readout would be transformative for this UK industry. We have demonstrated that capacitive touchscreen technologies can sense electrolytes in water drops placed directly on the touchscreen. Ions are particularly susceptible to the electric fringe field created by a capacitive touchscreen and we find a sensitive, near-linear response to their concentration at the required concentrations for nutrient monitoring. In this project, we propose to create the first application-specific proof-of-concept. In terms of the nutrients, the ions fall into two classes: redox and non-redox ions. These require different approaches to measurement with the touchscreen but for initial proof of concept we will focus on the non-redox macronutrients K+, Mg2+ and Ca2+. Working with the problem owner and industrial partner, we will firstly distinguish the anticipated requirements in terms of quantifying flows, target concentrations, sensing requirements and feedback loops, namely nutrient addition, diversion, fertigation-tracking, drainage, recycled and wastewater analysis. Secondly, we will functionalise the sensors to develop their selectivity. Thirdly, we will integrate into a partner site and optimise for manufacturability and usability. This enables potential for immediate and major impact across the UK through our partner institutes, contributing to sustainability goals and UK food and nutritional security needs.