SitS: Environmentally-benign sensors for the detection of nitrogen and foraging for nitrogen in soil

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This project will develop new sensing technologies to monitor and study nitrogen foraging by soil microbes that support crop plants. Next to carbon, nitrogen is the nutrient most necessary to all living organisms. Nitrogen is needed to produce the building blocks of life (e.g., DNA, proteins), and most nitrogen in aboveground living organisms is sourced from plants. To provide nitrogen for crops, worldwide in 2019, 107 million tons of nitrogen fertilizer were applied to agricultural fields. Yet less than half of applied nitrogen reaches crop plants, and much of the rest is converted by soil microbes into other forms of nitrogen, including gasses like nitrous oxide (N2O) that make significant contributions to global change. Increased understanding of how soil microbes forage for nitrogen is critical to sustainable agriculture and global change mitigation efforts. This proposal will develop non-destructive imaging technologies that sense nitrogen in soil and release nitrogen fertilizers in response to soil microbial signals. These tools will be used to assess nitrogen foraging by beneficial fungi that support crop plants. This project will enhance workforce development by training graduate and undergraduate students in interdisciplinary research through a Team Science course. This research will be integrated with teaching through educational modules for students in mass and energy balances, microbiology, and analytical chemistry courses, as well as providing senior chemical engineering design challenges. Knowledge from this work will be disseminated to the broader scientific community through a workshop at an international meeting.This research will develop new sensing technologies to monitor nitrogen in soils and apply them to study foraging of a model, focal microbe (arbuscular mycorrhizal (AM) fungi). Sensing technologies will be based on non-destructive Raman spectroscopy probes that sense nitrogen and hydrogels that sense compounds secreted by the AM fungi, resulting in nitrogen release. This research establishes the foundational knowledge and engineering design principles to support development of these technologies and establishes a foundation for future closed loop devices that would be capable of sensing nitrogen levels and releasing nitrogen on demand. This research has three objectives to: 1) Develop Raman probes that detect different forms of nitrogen in soil, 2) Evaluate foraging by AM fungi for different forms of nitrogen, and 3) Use an iterative approach to develop hydrogels that coat probes and release nitrogen when soil organisms are detected. Specifically, two sensors will be developed (Raman and hydrogel) that can be used independently or together to detect a biological function related to soil chemicals. The knowledge generated from this research could impact many fields. For example, in situ detection of nitrogen or nitrogen foraging has applications for precision farming. Raman probe nitrogen sensors could identify different nitrogen forms in soil spatially, in real time, and sensing hydrogels could release nitrogen on demand to fungi or plants based on their signaling molecules, potentially minimizing applied nitrogen loss in agricultural systems.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.