Monitoring Nitrogen Nutrition Stress in Tomatoes Using Impedance Spectroscopy

Nitrogen deficiency and excess in tomato plants impair yield and quality, with excess N increasing carcinogenic nitrate-to-nitrite conversion risk. Accurate, timely nutrient monitoring is essential for precise management. While optical sensors are widely used for N monitoring, they often lack accuracy for P and K. This study investigates electrical impedance spectroscopy as a method to assess N, P, and K status in tomato plants. Five tomato groups with varying N levels were grown in a greenhouse. Leaf N was measured, and impedance was recorded from 1 Hz to 1 MHz. An equivalent circuit model analyzed impedance changes with N content, identifying sensitive parameters for N status. Moisture effects were evaluated, and a predictive model for N content was developed. Results show electrical impedance spectroscopy effectively enables early diagnosis and monitoring of nitrogen stress in tomatoes.