Thesis
Continuous In-Situ Nitrate Determination with Ion Selective Electrodes
Masters by Research, Murdoch University
2023
Abstract
In-situ nitrate (NO3-) detection in agricultural soils has the potential to guide in-season fertiliser decisions to optimise crop yields. Decisions on application rates of nitrogen (N)-based fertiliser are based on potential grain profit, fertiliser prices and soil N levels (typically measured before or at seeding). Having real-time data on field NO3- levels will allow growers to make informed in-season decisions on strategic fertiliser applications. Current methods of in-situ NO3- detection use Ion Selective Electrode (ISE) sensors that have not been tested on Australian soils, where coarse-textured sandy soils and low moisture contents impede sensor functionality (low water filled pore space cause disconnects between soil water and ISE).
This research aims to assess sensor functionality in an array of soil textures with increasing clay content, mixed with a sandy soil typical of agricultural areas sourced from Badgingarra, Western Australia. Significant methodological development of the sensor was undertaken to create a comprehensive guide on improving reliability and reproducibility of the sensor. The sensors were subsequently tested in designed soils with clay contents of 5.8, 8.7, 9.8, 13.8, 21.6% and rewet to achieve moisture contents of 34, 56 and 100% water holding capacity (WHC).
Data analysis using backward multilinear regression showed a relatively strong predictive capacity (R2 = 0.77) associated with sensor output (mV), soil electrical conductivity (EC, dS/m), soil chloride (Cl-; mg/kg), clay content and moisture content. This initial testing demonstrates the potential functional capability for in-situ sensors to provide relatively reliable NO3- concentration predictions for a range of sandy soil textures with up to 22% clay, which could be used for guiding in-crop fertiliser decisions to optimise yield and fertiliser use efficiency. This research provides a basis for future development into stronger membrane construction, wireless field implementation and more accurate sensing.
Details
- Title
- Continuous In-Situ Nitrate Determination with Ion Selective Electrodes
- Authors/Creators
- Mitchell J Walton
- Contributors
- Fran Hoyle (Supervisor) - Murdoch University, Centre for Sustainable Farming Systems
- Awarding Institution
- Murdoch University; Masters by Research
- Identifiers
- 991005619760207891
- Murdoch Affiliation
- Centre for Sustainable Farming Systems; SoilsWest
- Resource Type
- Thesis
Metrics
60 File views/ downloads
129 Record Views