Soil composes the pedosphere, representing the dynamic interface between the hydrosphere, lithosphere, atmosphere, and biosphere. There are numerous processes involved in the pedosphere that affect the other environmental spheres. Among these processes, chemical and physical weathering of the minerals and rocks initiate soil formation, forming different soil attributes and resulting in specific soil types or horizons. The primary processes in the pedosphere are soil-forming factors like parent material, relief, climate, time, and organisms.
The combination of pedogenesis and weather is responsible for the manifestation of different physical and chemical attributes in different soil types, including variations of texture and color. To sum it up, weathering, landscape evolution, and pedogenesis can change the radionuclide concentrations and distributions in the pedosphere. The naturally occurring soil processes result in heterogeneous concentrations of radionuclides in the environment that can be detected by gamma-ray spectrometry.
The Importance of Gamma-Ray Spectrometry for Soil Mapping:
Geophysical methods like gamma-ray spectrometry are used for geological prospecting. They have demonstrated useful potential in soil science and soil mapping. Gamma-ray spectrometry is a geospatial technique that includes precise measurements of gamma-ray photon energies emitted by different radionuclides. It allows identifying the trace radioactive elements through gamma-ray emissions by naturally occurring radionuclides in the minerals, rocks, soils, and sediments. Uranium, potassium, and thorium emit radiation that generates gamma rays of short wavelengths in the electromagnetic spectrum.
Gamma-ray spectrometry maps the variation of soil minerals throughout the field by sensing the levels of natural radioactivity. The main advantage of gamma-ray spectrometry is the ability to define the management zones that contain different soil and mineral types to make variable-rate mapping easier and faster when combined with ground truthing. Also, another crucial factor is that the soil moisture conditions don’t affect the accuracy of the results. Some might balk at the idea of using radiation near themselves or their family members, but the kind of gamma-ray spectrometers SoilOptix® uses won’t hurt you or cause any negative effects. Only passive gamma sensors are used in agriculture. Gamma-ray spectrometers capture the natural level of radiation and do not emit any type of signal or energy themselves.
How does a Gamma-Ray Spectrometer Work?
Fine-scale spatial information on the soil properties is required to successfully implement precision agriculture. Proximal gamma-ray spectroscopy has evolved to be a promising tool for collecting fine-scale soil information. Different soil types contain different concentrations of radioactive uranium, thorium, and potassium. These elements are naturally equipped to help farmers and agronomists detect the different soil types and textures. The gamma-ray spectrometer is driven across a field attached to a ground machine and detects the low level of radiation emitted by these isotopes in the soil. The instrument is highly effective on the Smart Farm.
Depending on the soil mapping samples of each zone or the soil type and the yield goal in every zone, it is possible for the agronomists to calculate and estimate how much fertilizer or other inputs to be used in each zone. The purpose of any type of sensing is to study the field variability and translate that field variability analysis into a type of management decision.
A Relatively New Approach in Soil Mapping:
Characteristics of spatial variability in soil properties are critical for farmers to reduce the risk of crop failure and improve decision-making efficiency. This is beneficial in both economic and environmental sense. Collecting fine-scale information on soil properties through conventional soil sampling and laboratory analysis is time-consuming and expensive. Better and more efficient methods to get this information are crucial for soil monitoring, modeling, and precision agriculture.
Gamma rays are quanta or photons of high energy and short wavelength electromagnetic radiation emitted from naturally occurring isotopes. Radioactive isotopes of the elements that emit gamma radiation are known as radionuclides. Most radionuclides occur naturally, but only potassium, uranium, and thorium produce enough gamma rays of sufficient energy to be measured with gamma-ray spectroscopy.
There is no denying that Gamma-ray spectroscopy is one of the best and most effective methods of soil mapping and soil modeling. For soil science, gamma-ray spectrometry is of a specific value because it detects a signal from the landscape surface and integrates the information over a specific value. Apart from that, different spatial scales can be covered through ground-based or airborne sensing techniques. Together with other remote sensing methods, gamma signatures can offer comprehensive information to understand the land-forming processes and soil mapping.