An ISE-based On-Site Soil Nitrate Nitrogen Detection System.

Area of Science:

• Agricultural Science
• Environmental Science
• Analytical Chemistry

Background:

• Soil nitrate-nitrogen (NO₃⁻-N) is crucial for nitrogen topdressing applications.
• Ion-selective electrode (ISE) methods offer rapid, low-cost in-field detection but face accuracy concerns due to simplified sample preparation.

Purpose of the Study:

• To develop and validate a prototype system for on-site soil NO₃⁻-N detection.
• To assess the accuracy, stability, and efficiency of the developed system compared to laboratory methods.

Main Methods:

• A self-designed prototype system utilizing spinning centrifugation to minimize slurry interference.
• A modified Nernstian prediction model integrating outputs from ISE and soil moisture sensors.
• Validation against standard laboratory ISE detection and spectrometric methods.

Main Results:

• The sensor fusion model achieved measurement accuracy comparable to laboratory ISE detections.
• Average absolute error (AE) and root-mean-square error (RMSE) were below 4.7 and 6.1 mg/L, respectively, compared to the spectrometric method.
• On-site testing efficiency was 4-5 min/sample, a 60% reduction in operation time.

Conclusions:

• The developed ISE-based system demonstrates a promising capability for dynamic on-site monitoring of soil NO₃⁻-N.
• The system provides accurate and efficient soil nutrient status assessment, supporting optimized agricultural management.
• Continuous monitoring revealed a declining peak of NO₃⁻-N over 42 days.