In Situ Rapid Detection of Soil Nitrate Nitrogen via Dielectric Spectroscopy Using a Dual-Band Frequency-Splitting...

Area of Science:

• Agricultural Engineering
• Soil Science
• Sensor Technology

Background:

• Traditional soil nitrate nitrogen (NO₃⁻-N) detection is slow and prone to interference.
• Accurate, real-time NO₃⁻-N monitoring is crucial for crop growth and nitrogen management.

Purpose of the Study:

• To develop a novel sensor for rapid, in situ soil NO₃⁻-N detection.
• To overcome limitations of traditional methods, including timeliness and matrix interference.

Main Methods:

• A dual-band frequency-splitting coupled sensor with a concentric copper ring structure was designed.
• Dielectric spectroscopy utilized low-frequency bands for water/salinity isolation and high-frequency bands for NO₃⁻-N signal capture.
• Field trials conducted across five diverse soil types.

Main Results:

• The sensor achieved high accuracy (R² 0.943-0.987) with low errors (MAE ≤0.75 mg/kg, RMSE ≤0.92 mg/kg).
• Millisecond-level response times were recorded, with minimal signal drift (<0.25 mg/kg) under extreme conditions.
• Excellent correlation (r=0.995-0.999) observed in typical agricultural scenarios.

Conclusions:

• The developed sensor offers a rapid, precise, and interference-resistant alternative for soil NO₃⁻-N detection.
• It significantly reduces analysis time from days to milliseconds, enabling dynamic nitrogen management.
• The sensor's IoT integration potential supports smart agriculture and sustainable development.