Assessing canopy temperature responses to nitrogen fertilisation in South Indian crops using UAV -based thermal sensing

authored by

Albara Almawazreh, Andreas Buerkert, Prem Jose Vazhacharickal, Stephan Peth

Abstract

The heavily strained water resources in Bengaluru, India, as a result of rapid urban expansion are increasingly at risk of overexploitation and pollution due to intensified agriculture practices, such as increased nitrogen (N) use and irrigation. In recent years, thermal cameras mounted on Unmanned Aerial Vehicles (UAVs) have proven useful in detecting crop water stress and managing irrigation. However, the use of these cameras in managing N fertilization in the subtropics has been understudied. We employed this technology in two agricultural field experiments in Bengaluru to study the effects of N fertilization on canopy temperatures of maize, finger millet, and lablab, and their correlations with Leaf Chlorophyll Content (LCC), and soil temperature. The results showed that the effect of N was more pronounced at the rainfed experimental site, where the soil is highly acidic and porosity is low. At this site, N significantly affected the canopy temperature of maize and finger millet, particularly under sunny conditions (p = 0.000245), resulting in plots receiving higher nitrogen dosages showing canopies with 2.1°C and 1.3°C cooler temperatures, respectively. Lower temperatures with higher N application were also observed in the irrigated experiment (p value = 0.118), albeit only under sunny conditions. Additionally, canopy temperatures and LCC significantly correlated for maize (R = -0.68, p = 0.015) in the rainfed experiment and millet (R = -0.7, p = 0.011) in the irrigated experiment. However, the correlation of LCC with NDVI was stronger on both sites. Canopy and soil temperatures correlated significantly only when analysed without considering crop species. The use of thermal cameras, equipped with uncooled microbolometers, is accompanied by the dilemma of temperature drift, which affect measurement accuracy. We introduced a drift correction process, which effectively reduced drift by up to 45%, and decreased the drift standard deviation to less than 1°C, that resulted in homogeneous thermal maps suitable for robust statistical analysis. In my submission i added keywords, are they going to be included in the publication ??.

Organisation(s)

Institute of Earth System Sciences

External Organisation(s)

University of Kassel
University of Agricultural Sciences, Bangalore

Type

Article

Journal

International Journal of Remote Sensing

ISSN

0143-1161

Publication date

2025

Publication status

Accepted/In press

Peer reviewed

Yes

ASJC Scopus subject areas

General Earth and Planetary Sciences

Sustainable Development Goals

SDG 11 - Sustainable Cities and Communities

Electronic version(s)

https://doi.org/10.1080/01431161.2025.2452312 (Access: Open)