There is a compelling need for more efficient food production; 20% of farmland is now degraded due to over-intensive farming, only 6% of agricultural dry biomass gets eaten and the human population continues to rise. This need has fuelled the adoption of precision farming with point-of-use (PoU) sensors. In Chapter 1, I introduce the topic of this thesis by reviewing the PoU sensing mechanisms and devices that are emerging using cellulose fabrics, I then highlight the trends in recent applications.

In Chapter 2, I present a low-cost method to grow metals such as Au, Ag and Pt autocatalytically inside the fibrous networks of cellulose fabrics. I demonstrate a range of applications including an electrochemical biosensor that uses metallised paper to measure DNA biomarkers of Mycobacterium avium spp. Paratuberculosis, the causative agent of Johne’s disease that affects ruminant animals such as cattle and sheep. In the future, this method of fabric metallisation may pave the way for new classes of PoU devices in life science and agricultural applications.

In Chapter 3 I dive into soil nutrients. Most farmers have no way to measure their fertiliser requirements, so practical guidance leans toward over-fertilisation, to maximise yields. I demonstrate a robust and selective PoU NH4+ sensor that measures 3±1ppm in soil (R2=0.70), and a machine learning model that predicts NO3- (R2=0.87) from only PoU and weather data. Finally, I show how a recurrent neural network predicts NH4+ and NO3- up to 12 days into the future. The outlook is that farmers, with little or zero access to soil measurements, can predict crucial soil nutrients with enough accuracy to reduce over-fertilisation or improve crop yields.

In closing, I consider the outlook for PoU sensors with cellulose fabrics in agriculture, the central role they will take in food production and the challenges they must overcome.