Abstract

Soil nitrate (NO3) exhibits rapid spatial and temporal variability that conventional point-sampling methods cannot effectively capture, limiting timely nutrient management and plant stress detection. This study aimed to validate a low-cost, threedimensional- printed electrochemical NO3 sensor for continuous in-soil monitoring and to evaluate whether sensor-derived NO3 dynamics reflect plant physiological responses. For this purpose, cotton (Gossypium hirsutum L.) plants were grown in pots under greenhouse conditions. The sensor was evaluated in two sequential phases: an initial calibration phase to characterize sensor response across a broad NO3 concentration range, followed by a validation phase in the cotton plant rhizosphere. In the calibration phase, the sensor exhibited a sensitivity of −73.99 mV/dec and a limit of detection of 0.12 ppm. In the validation phase, cotton plants were grown under three NO3 treatment levels: no NO3 (0 ppm), low NO3 (150 ppm), and high NO3 (250 ppm), with three replicate pots per treatment. Sensor NO3 measurements were validated against commercial grade Ward Laboratory data obtained from the same soil samples. Our sensor accurately captured fertilizer-induced NO3 spikes and depletion trends and showed strong agreement with laboratory measurements (R2 = 0.89, root mean square error = 14.77 ppm). F-score, coefficient of variation, and Tukey’s honestly significant difference post hoc analyses confirmed a clear distinction between fertilized and unfertilized soil following NO3 application. Furthermore, cotton plants’ physiological parameters, such as leaf area index (LAI), chlorophyll index, and stomatal conductance, were measured and correlated with soil NO3 concentrations. LAI and chlorophyll index increased withNO3 availability, indicating enhanced canopy development and leaf nitrogen status. In contrast, stomatal conductance decreased with increasing NO3, reflecting physiological stress under excessive or sudden NO3 supply. These results demonstrate that the sensor provides chemically accurate and biologically meaningful NO3 measurements, supporting its potential for precision nutrient management and future field-scale agricultural deployment.

Description

This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License (http://creativecommons.org/licenses/by-nc-nd/4.0/), which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made. © 2026 The Author(s).

Publisher

WILEY

Date of publication

8-2026

Language

english

Persistent identifier

http://hdl.handle.net/10950/5197

Document Type

Article

Download

Included in

Engineering Commons

Share

COinS