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EAGER SitS: Underground Radio Frequency Wireless Network for Measuring Soil Moisture over Large Spatial Scales


<p>Ensuring adequate food and water resources for an increasing population is one of the major challenges of the 21st century. Our abilities to do this are highly dependent on how efficiently soil and water natural resources are managed. In addition, water stored in the soil changes considerably over space and time, and it is difficult to measure these variations. This is important because water variations in soil reservoirs affect the Earth's climate system, have large influences on cloud formation and precipitation, and affect utilization of the Sun's energy. An ability to accurately measure soil water content variations over the landscape will enable us to improve agricultural yields, increase food security, better manage water from rainfall (particularly intensive storms), which is important in urban planning and management. The proposed research work will create an inexpensive, wireless, scalable, fully buried system for frequent measurements of soil water in field environments by using underground radio frequency (RF) transmissions. The research brings together scientific expertise from different disciplines, thus enabling collaboration among soil scientists, engineers, and computer scientists to create an "internet-of-things" for ultimate use in managing our limited water and soil resources and helping ensure food security and societal well-being.<br />
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Soil water is one of the most important factors that affects plant productivity. One of the grand challenges in soil moisture monitoring is to capture the natural heterogeneity of the soil-hydrological system at scales of 1 to 1000 m2. This intermediate scale between point-scale and available remote sensing measurement scales is important for determining impacts on ecosystem services as well as for improving the use of water resources with environmentally sustainable management practices. Currently, there are few methods for scaling soil moisture from very limited numbers of point-scale measurements to larger scales (field, watershed to regional). As a result, errors and biases are introduced in land surface, hydrological, and vegetation models, and in determining soil saturation and rainfall-runoff responses in catchments. It also handicaps the development of precision and sustainable agriculture. Our objectives are to explore the development of an inexpensive, wireless, scalable, fully buried sensor network system using underground radio frequency (RF) transmission for measurements of soil moisture over 1 to 1000 m2 spatial scales and high temporal resolution and to evaluate the potential for this technology to serve as an accurate sensor in soils. This technology, if successful, could enable soil scientists to gain a better understanding of the complex soil system, its dynamics, and its biological, chemical, and physical processes. We will use the attenuation of RF signal that propagate inside soil to infer water content in the soil column above the sensor. In this project, we will create a wireless cyberphysical sensor network with approximately 40 nodes and implement it at a field site in Illinois with highly-characterized soils for evaluation of concepts. Network development includes hardware, firmware, and user interface. The RF nodes will be buried in the field at about 25 cm deep to sense the water content between the RF node and the soil surface. Data analysis will focus on the correlation between soil moisture and changes in the wireless signal strength transmission. Other factors, such as plant canopy height and root conditions, will be included in machine learning algorithms to establish a robust model. The cyberphysical sensing network will be relevant to many scientific and engineering applications, including use by hydrometeorologists interested in land-atmosphere interactions, by hydrologists for determining soil saturation for agricultural purposes, drought monitoring, irrigation scheduling, and flash flood forecasting, by water supply managers, and by scientists involved in weather and climate research. This research has potential to influence development of new sensing technologies in the future. The highly multidisciplinary nature of the research will bring together soil scientists, computer scientists, and research engineers to explore development of a novel "internet of things" for use in managed and unmanaged soils.<br />
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This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.</p>

Xufeng Zhang; Roser Matamala Paradeda; Supratik Guha
University of Chicago
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