Tabitha Brown

Tabitha Brown
  • PhD Candidate
  • Washington State University
  • Crop and Soil Sciences

Advisor: 

Dave Huggins

Thesis or Dissertation Citation: 

Brown, T. 2015. Variable rate nitrogen and seeding to improve nitrogen use efficiency. Washington State University PhD Dissertation.

Research Focus: 

Impact of agricultural management practices on soil health, productivity, & nutrient use efficiency

Research Abstract: 

Increased nitrogen (N) fertilizer additions to agricultural cropping systems may be necessary to feed a growing world population but will also require greater nitrogen use efficiency if agroecosystems are to continue to provide certain ecosystem services (e.g., greenhouse emission reductions or mitigation). Site-specific N fertilizer management has been reported as an important strategy to increase NUE in modern cropping systems. However, site-specific management requires knowledge of the spatial variability in soil properties, crop physiological response, and drivers of N cycling across heterogeneous landscapes. The Palouse region of eastern Washington, USA is characterized by complex soil fertility and crop productivity patterns but cropping systems are typically managed uniformly. The overall research goals were to investigate winter wheat (Triticum aestivum) yield-water-nitrogen use efficiency (NUE) relationships across landscape positions that differ in soil properties and historical yield. Field studies were conducted during the 2010, 2011 and 2012 winter wheat harvest years to evaluate nitrogen fertilizer and seeding rate effects on soft white winter wheat (cv. 'Chukar') yield and performance. The experiment was designed as a randomized complete block split plot design with nitrogen fertilizer rate (0, 40, 80, 120, 160 kg ha-1) as the main plot and seeding rate (80, 165, 250, 335 seeds m-2) as the subplot. The experiment was conducted at the Cook Agronomy Farm, near Pullman, WA. Soil and crop physiology based nitrogen use efficiency components and indices were determined (Huggins and Pan, 1993) and used to develop performance classes for winter wheat to aid in site-specific N fertilizer and seeding rate management decisions for the region.

Biography: 

Tabitha is a PhD candidate in Soil Science at Washington State University. She is a graduate fellow in the NSPIRE IGERT program (Nitrogen Systems: Policy-oriented Integrated Research and Education). Tabitha has a master’s degree in Soil Science from WSU; her thesis, "Characterizing and managing stratified soil acidity in inland Pacific Northwest Direct-seeded Cropping Systems." In 2002, she received her bachelor’s in Environmental Science (Soil Science concentration) from North Carolina State University.

Publications and Presentations: 

Eitel, J., Magney, T., Vierling, L, Brown, T., Huggins, D. 2014. LiDAR based biomass and crop nitrogen estimates for rapid, non-destructive assessment of wheat nitrogen status. Field Crops Research. 159: 21-32.