This award was made through the "Signals in the Soil (SitS)" solicitation, a collaborative partnership between the National Science Foundation, the United States Department of Agriculture National Institute of Food and Agriculture (USDA NIFA) and the following United Kingdom Research and Innovation (UKRI) research councils: 1) The Natural Environment Research Council (NERC), 2) the Biotechnology and Biological Sciences Research Council (BBSRC), 3) the Engineering and Physical Sciences Research Council (EPSRC), and the Science and Technology Facilities Council (STFC). The research project is a collaboration between Tufts University in the U.S. and the U.K. institutions of Keele University and the University of Birmingham. Advancing our understanding of the soil ecosystem, especially the dynamics of nitrogen-containing species, such as ammonium and nitrate, is critical to improving soil fertility, increasing crop productivity, managing greenhouse gas fluxes, and protecting the water and environment. The researchers will development a next generation, integrated sensing system for in-field, large area, high resolution monitoring of nitrogen species, soil moisture, potassium, and salinity. The wireless Distributed Real Time Soil (DiRTS) monitoring network is comprised of (1) soil sensor nodes that mimic plant root-like water intake, (2) robust sensors for soil ammonium, nitrate, potassium, moisture, and salinity levels (3) ultra-low power circuit architectures for readout and digitization, (4) long range wireless data communication, and (5) advanced algorithms for mapping of soil nitrogen, potassium, salinity, and moisture levels. The platform will address fundamental weaknesses in our understanding and control of nitrogen species in both unmanaged (e.g. forest) and managed (e.g. agriculture) soils. Beyond the technical impact, the proposed research effort will offer education and training opportunities for undergraduate and graduate students through new curricula. Farmers and other soil management practitioners will benefit through publicly-available training modules on the design and deployment of the wireless Distributed Real Time Soil (DiRTS) monitoring platform.

The DiRTS platform will make several notable scientific contributions: (1) Continuous capillary-driven sampling of the target soil nutrients mimicking the natural water intake by roots and transpiration through aboveground plant parts; (2) Ion-sensitive electrodes utilizing embedded desalination to improve selectivity, and utilizing redundancy and Bayesian calibration to improve sensitivity; (3) Circuits for readout and digitization operating below 0.5 V power supply and nanowatt level power dissipation; (4) Event-driven sampling and wireless communication using probabilistic sensor scheduling based on available power and data importance; and (5) State of the art statistical machine learning-based approaches for generating high resolution spatio-temporal chemical maps from irregularly sampled data. All technology will be validated using in-situ measurements in an experimental forest. Specifically, experiments will be performed to quantify nitrous oxide fluxes via a greenhouse gas analyzer and mapping using the DiRTS sensor network. This research project brings together experts in engineering, biogeosciences, and chemistry from the U.S. and U.K., with strong backgrounds and expertise in relevant areas of sensing, electronics, microfluidics, biogeochemistry, signal processing, and sensor networks. The DiRTS platform will advance our understanding of soil nitrogen dynamics and provide a method to help manage these dynamics for more economic and environmentally-sustainable agriculture practices.

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.

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Tufts University
United States
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