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Development of On-the-go Nitrogen Application Algorithms for Cotton

Development of On-the-go Nitrogen Application Algorithms for Cotton. Terry Griffin, Ph.D., CCA Assistant Professor – Economics Dept. of Agricultural Economics & Agribusiness. NEU Conference. Motivation and Issue. Analyses have been conducted for single datasets

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Development of On-the-go Nitrogen Application Algorithms for Cotton

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  1. Development of On-the-go Nitrogen Application Algorithms for Cotton Terry Griffin, Ph.D., CCA Assistant Professor – Economics Dept. of Agricultural Economics & Agribusiness NEU Conference

  2. Motivation and Issue • Analyses have been conducted for single datasets • Failed to model multiple climates, systems, etc. • Global response estimated from pooled dataset • Derive on-the-go nitrogen application algorithms Objective: analyze multi-state experiment data to estimate response between active sensor reflectance and cotton yield for on-the-go nitrogen management • Develop on-the-go N application algorithm

  3. Data and Methods • Pooled model • Multiple site-years; 13 states • All data (sites and years) in single dataset • Each sub-dataset controlled for heterogeneity • Testing for heterogeneity between sub-datasets • Correlation among • yield, nitrogen rate, NDVI values and timing • Regression analysis of pooled dataset

  4. Challenges • Cotton in a perennial • N rate sufficient to cause yield penalty • Identifying appropriate timing for NDVI • DAP, GDD60 • Testing functional forms of relationships • Testing indexes for algorithm • Variety, location, and GDD60 specific • Global algorithm with local intercept/slope shifters

  5. Correlation Coefficients

  6. Cotton Yield Response to Applied N • Theoretically quadratic; without plateau

  7. Cotton yield by N rate: 7 site-years

  8. NDVI by N rate

  9. NDVI wrt N rate by Timing

  10. Summary and Future Work • Analysis is on-going • Have not determined optimum algorithm • Use of GDD60 needs to be revisited

  11. Acknowledgements • Funding from Cotton Inc. • Collaborators in respective states • John Kelley – Graduate Student

  12. Terry Griffin Assistant Professor - Economics 501.671.2182 tgriffin@uaex.edu

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