Measuring soil moisture using P-band radiometry

Have you ever wondered why the possibility of life on any other planet is bleak? It is because our beautiful Earth has rich soil with liquid water which makes life possible.

Soil is the living skin of the Earth, and can be described as the interface between biology and geology. It is the water in soil that keeps the earth’s biota alive. Timely information on soil moisture is required to monitor and forecast agricultural droughts, wildfires, flood risk areas, landslides, etc.

The ability to measure soil moisture accurately is important in domains spanning agriculture, hydrology, and meteorology. In agriculture, it is useful for irrigation scheduling, seed germination and crop yield forecasting. In hydrology, partitioning of rainfall into its runoff and infiltration components depends on soil moisture. Improvement in the prediction of essential climatic variables like rain, temperature, humidity etc., is possible by incorporating accurate soil moisture in weather forecasting models.

Soil moisture is generally measured using L-band radiometry. This remote sensing approach has now been widely accepted as a state-of-the-art method, and has been adopted by leading global soil moisture dedicated satellite missions like Soil Moisture and Ocean Salinity (SMOS) and Soil Moisture Active Passive (SMAP).

My research project at the IITB-Monash Research Academy seeks to go beyond L-band radiometry to P-band radiometry, which is a longer wavelength measurement that provides the potential to retrieve deeper soil moisture information. P-band radiometry hopes to do so more accurately due to reduced soil roughness and vegetation effects. However, there are very few articles available in literature to support this hypothesis.

Figure 1. a. Field data measurements for modelling; b. Sunset at our experimental field at Cora Lynn where radiometers operating at well-established L-band (1.4 GHz) and first-of-its-kind P-band (0.75 GHz) are tower-mounted.

Any new satellite technology requires a huge amount of groundwork to test the science and technology that will be put into operation. My research is one of the first few drops in the ocean in this arena of being able to remotely sense deeper depth soil moisture. A self-contained experimental set-up has been established in an agricultural farm at Cora Lynn, Victoria from where the crucial input data for my model comes in. It is anticipated that future satellites will be designed for P-band radiometers, which will use my model to study soil moisture.

We, graduate research scholars of the IITB-Monash Research Academy, study for a dually-badged PhD from IIT Bombay and Monash University, spending time at both institutions to enrich our research experience. The Academy is a collaboration between India and Australia that endeavours to strengthen relationships between the two countries. Its CEO, Prof Murali Sastry says, “The IITB-Monash Research Academy represents an extremely important collaboration between Australia and India. Established in 2008, it is now a strong presence in the context of India-Australia collaborations.”

The area that I am working in is a relatively new direction of research in soil moisture study, and I am hoping that this research will be of help to a variety of users like space agencies, the common man, as well as scientists.

For space agencies like NASA, ESA, ISRO, CESBIO in particular, this work will help them understand and implement future missions for deeper depth soil moisture. To a common man, the data from such a satellite can be processed and produced as maps with which farmers can plan to irrigate their fields, thus knowing more about the already existing water under the surface. To climate research scientists, it can help them to improve their models and forecasts. It also helps in meeting the challenges in water governance.

Moving forward, I’m hoping that you will not just see the soil but will definitely feel it as a RESOURCE!