Plant root study in agricultural settings with the use of geophysical methods

Gerea, Alexandra Georgiana ORCID: 0000-0002-6526-4934 (2024). Plant root study in agricultural settings with the use of geophysical methods. University of Birmingham. Ph.D.

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Abstract

The thesis represents a multidisciplinary approach to explore how geophysical methods can analyse plant roots in agricultural settings. It delves into the study of plant roots, examining their varieties, complexities, and significance in agriculture, as well as their behaviours. This is followed by an examination from the perspective of the geophysical methods, more specific ground penetrating radar (GPR) and resistivity, focusing on the methods themselves, the theoretical aspects, and a literature review of their application in agriculture, soil, and root studies.
The goal was to lay the groundwork for conducting geophysical surveys in actual agricultural contexts and to comprehend root behaviours through the lens of geophysical methods, taking into account their biological and physical complexity. The innovation comes from adapting the experimental settings so that they could come as close as possible to real-world agricultural environments and their specific characteristics, which could have practical applications in real world settings.
Direct measurements in the field were undertaken to understand the limitations and the behaviour of the environment and roots in a real world agricultural setting and thereby enhancing the application of geophysical methods. Both outdoor and indoor experimental surveys were conducted, under various conditions and types of plants using both the GPR and the resistivity methods.
Models were developed to not only understand the methods' limitations but also to simulate various conditions for better insight into root and soil behaviours when applying these
methods. A transparent soil was innovated and tested in the laboratory to improve correlation between objectives and data anomalies during resistivity surveys.
Various electrical devices were constructed and used, including the use of IoT sensors and a prototype for rapid resistivity surveys capable of collecting data from all the possible combinations of electrodes at different frequencies.
It has been observed that agricultural environments pose unique challenges and the use of high-frequency GPR antennas (1.5 GHz and 4 GHz) or small electrodes closely spaced entails limitations in real-world agricultural settings. However different areas have been highlighted and correlated with the root area but no individual roots of the agricultural plants with fine roots.
The models have allowed to understand how the resistivity areas modify the way root areas can be detected, and different arrays being more suitable for these kind of studies, whereas from the point of view of the GPR method the limitations appearing when the roots have closer permittivity values to the soil which represents a very plausible and common limitations.
The study suggests a shift in focus from individual roots to active root zones, understanding their dynamic behaviours influenced by environmental variables (e.g., watering or soil drainage). Roots are living objectives which grow, change paths, tend to absorb moisture around their roots, etc. all of these changing the way they can be identified with geophysical methods in different scenarios. More prominent observations have been made especially with the resistivity method where roots can change the resistivity values of the soil they grow in and its surroundings depending on watering time and drainage.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):