Analysis of Plant Conductivity and Resistance as Indirect Indicators of Nutrient Content Using Relaxation Oscillators

Muhammad Nur Aufa Alghozi; Supardi Supardi

doi:10.17509/wafi.v11i1.879

Authors

Muhammad Nur Aufa Alghozi Physics Education Department, Universitas Negeri Yogyakarta, Indonesia
Supardi Supardi Physics Education Department, Universitas Negeri Yogyakarta, Indonesia

DOI:

https://doi.org/10.17509/wafi.v11i1.879

Keywords:

Resistive sensor, plant nutrients, electrical conductivity, relaxation oscillator

Abstract

Real-time monitoring of plant nutrient status is essential for optimizing fertilization in precision agriculture. This study evaluated electrical conductivity and resistance as indirect indicators of nitrogen (N), phosphorus (P), and potassium (K) nutrient content in avocado plants (Persea americana) using a low-cost resistive sensor system. The system features a relaxation oscillator circuit integrated with an Arduino Uno microcontroller to convert plant resistance into frequency signals, with an AC-based method implemented to mitigate DC polarization effects in biological tissues. A 14-day comparative experiment was conducted using two avocado plants: Plant A, which received NPK 16-16-16 fertilizer daily, and Plant B, an unfertilized control. Data were collected via stainless steel electrodes inserted into the plant stems. Results demonstrated that NPK fertilization consistently increased plant conductivity and decreased electrical resistance in Plant A (average: 20,841.72 Ω), while Plant B maintained comparatively higher and more stable resistance values (average: 24,309.24 Ω) throughout the observation period. The sensor system also detected physiological stress symptoms in Plant A from Day 11 onward, corroborated by visual observations of fertilizer toxicity. These results confirm that electrical resistance serves as a reliable indirect indicator of relative nutrient levels, offering a practical, economical, and non-destructive approach for real-time plant monitoring in precision agriculture.

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