Research on Soil Inorganic Nitrogen Detection Technology Based on Dielectric Response

Zhenyu Jia, Xuan Han, Ri Hu, Jiangyang Yu, Xiaoqing Yan and Jinghui Xu ()
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Zhenyu Jia: College of Water Conservancy and Construction Engineering, Northwest Agricultural and Forestry University, Yangling 712100, China
Xuan Han: College of Water Conservancy and Construction Engineering, Northwest Agricultural and Forestry University, Yangling 712100, China
Ri Hu: College of Water Conservancy and Construction Engineering, Northwest Agricultural and Forestry University, Yangling 712100, China
Jiangyang Yu: College of Water Conservancy and Construction Engineering, Northwest Agricultural and Forestry University, Yangling 712100, China
Xiaoqing Yan: College of Water Conservancy and Construction Engineering, Northwest Agricultural and Forestry University, Yangling 712100, China
Jinghui Xu: College of Water Conservancy and Construction Engineering, Northwest Agricultural and Forestry University, Yangling 712100, China

Sustainability, 2025, vol. 17, issue 6, 1-12

Abstract: Efficient monitoring of soil inorganic nitrogen is crucial for precision agriculture fertilization and ecological environmental protection. Traditional detection methods are complex and challenging for real-time in situ measurements. This study proposes an innovative approach based on dielectric response characteristics, enabling non-destructive and rapid detection by analyzing soil polarization behavior in an electromagnetic field. Using a vector network analyzer (E5071-C), we systematically measured the complex dielectric spectra of red soil and yellow clay loam across a wide frequency range from 10 MHz to 4.5 GHz. Coupled with water–nitrogen interaction experiments (volume water content: 0.05–0.25 cm 3 /cm 3 ; nitrogen concentration: 0–0.2 mol/L), we established a high-frequency–low-frequency collaborative detection model. The study found that at the 3.8 GHz high-frequency band, the interface polarization weakening effect allows for the precise measurement of soil water content (R 2 = 0.82; RMSE = 0.030 cm 3 /cm 3 ). In the 100–200 MHz low-frequency band, based on ion migration dynamics, we successfully identified characteristic sensitive frequency bands for NH 4 + (136–159 MHz) and NO 3 − (97–129 MHz). Notably, at 127 MHz, the water–nitrogen coupling model predicted inorganic nitrogen content with a determination coefficient of 0.721. This method effectively overcomes the water interference issue inherent in traditional single-frequency dielectric methods through a dual-frequency decoupling mechanism. The findings lay a theoretical foundation for developing in situ sensors for farmland. Real-time monitoring can significantly improve nitrogen fertilizer utilization efficiency and reduce environmental pollution, offering substantial application value for advancing precision agriculture and sustainable development.

Keywords: dielectric measurements; soil inorganic nitrogen; dielectric constant (search for similar items in EconPapers)
JEL-codes: O13 Q Q0 Q2 Q3 Q5 Q56 (search for similar items in EconPapers)
Date: 2025
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