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The U.S. Department of Agriculture–Agricultural Research Service (USDA-ARS) has been a leader in weed science research covering topics ranging from the development and use of integrated weed management (IWM) tactics to basic mechanistic studies, including biotic resistance of desirable plant communities and herbicide resistance. ARS weed scientists have worked in agricultural and natural ecosystems, including agronomic and horticultural crops, pastures, forests, wild lands, aquatic habitats, wetlands, and riparian areas. Through strong partnerships with academia, state agencies, private industry, and numerous federal programs, ARS weed scientists have made contributions to discoveries in the newest fields of robotics and genetics, as well as the traditional and fundamental subjects of weed–crop competition and physiology and integration of weed control tactics and practices. Weed science at ARS is often overshadowed by other research topics; thus, few are aware of the long history of ARS weed science and its important contributions. This review is the result of a symposium held at the Weed Science Society of America’s 62nd Annual Meeting in 2022 that included 10 separate presentations in a virtual Weed Science Webinar Series. The overarching themes of management tactics (IWM, biological control, and automation), basic mechanisms (competition, invasive plant genetics, and herbicide resistance), and ecosystem impacts (invasive plant spread, climate change, conservation, and restoration) represent core ARS weed science research that is dynamic and efficacious and has been a significant component of the agency’s national and international efforts. This review highlights current studies and future directions that exemplify the science and collaborative relationships both within and outside ARS. Given the constraints of weeds and invasive plants on all aspects of food, feed, and fiber systems, there is an acknowledged need to face new challenges, including agriculture and natural resources sustainability, economic resilience and reliability, and societal health and well-being.
Livestock rations are formulated to minimize feed cost subject to nutritional requirements for a target performance level, which ignores the potentially substantial cost of disposing of nutrients fed in excess of nutritional requirements. We incorporate nutrient disposal costs into a modified least-cost ration formulation model to arrive at a joint least-cost decision that minimizes the sum of feed and net nutrient disposal costs. The method is demonstrated with phosphorus disposal costs on a representative dairy farm. Herd size, land availability and proximity, crop rotation, and initial soil phosphorus content are shown to be important in determining phosphorus disposal costs.
Drip tests designed to replicate the synergistic interactions between waste
glass, repository groundwater, water vapor, and sensitized 304L stainless
steel in the potential Yucca Mountain Repository have been ongoing in our
laboratory for over ten years. Results will be presented from three sets of
these drip tests: two with actinide-doped glasses, and one with a
fully-radioactive glass. Periodic sampling of these tests have revealed
trends in actinide release behavior that are consistent with their
entrainment in colloidal material when as-cast glass is reacted. Results
from vapor hydrated glass show that initially the actinides are completely
dissolved in solution, but as the reaction proceeds, the actinides become
suspended in solution. Sequential filtering and alpha spectroscopy of
colloid-bearing leachate solutions indicate that more than 80% of the
plutonium and americium are bound to particles that are captured by a 0.1 μm
filter, while less than 10% of the neptunium is stopped by a 0.1 μm filter.
Analytical transmission electron microscopy has been used to examine
particles from leachate solutions and to identify several actinide-bearing
phases which are responsible for the majority of actinide release during
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