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Predominant N Management Issues

Improving NUE in Corn With Crop Sensing: Reflections, Concerns, and Needed Research Rain fed Southern Corn Belt. Predominant N Management Issues. Soil variability (some fields and soil types will be much better suited for sensor-driven N applications) alluvial >> loess > claypan

carolyn-mcmahon
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Predominant N Management Issues

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  1. Improving NUE in Corn With Crop Sensing: Reflections, Concerns, and Needed ResearchRain fed Southern Corn Belt

  2. Predominant N Management Issues • Soil variability (some fields and soil types will be much better suited for sensor-driven N applications) alluvial >> loess > claypan • Balance between meeting early N corn needs and not adding too much early such that the plant poorly predicts what the soil will provide • If weather cooperates, N will be fall applied setting up a scenario of potential N loss

  3. Predominant N Management Issues • Excessive spring and early summer rainfall setting up the need for a rescue • Opportunity of application (can be especially narrow for poorly drained soils like the claypan soils) • Hard to match side-dress UAN with preplant AA performance (source & placement issues) • Hot & Dry weather (if only all growing seasons were like 2004) • Shift of C-S to C-C with feed-to-fuel market shifts

  4. Scenarios that best fit sensor-driven N fertilizer applications: • Fields following wet spring and early summer (loss of fall applied N) • Fields that have received recent manure applications and uncertainty exists for how much N is available • Fields receiving uneven N fertilization (fertilizer or manure) • Fields coming out of pasture, hay, or CRP • Fields with extreme variability in soil type • Fields of corn-after-corn when drought occurred the first year (i.e. non-uniform carry over)

  5. Other Thoughts and Reflections

  6. What will the impact of public funding be on the future of VR N management?

  7. Can a small nitrogen-rich reference area serve a large, variable field? • Will we eventually get by without a reference area within each field?

  8. Yield efficiency (or NUE) not the same at EONR

  9. Issues of a changing EONR and reporting results

  10. Yield efficiency related to EONR for 2004 fields 3.6 12.8

  11. Profile inorganic N related to EONR for 2004 fields 3.6 12.8

  12. When it comes to sensor indices…. • Some indices stretch out differences better than others: CHL index ~ simple ratio > NDVI • Nice to have sensors output either Vis or NIR for purposes of indice performance testing • NDVI and the simple ratio are mathematically related NIR- VIS NDVI = -------------------- NIR +VIS Vis simple ratio = --------------- NIR

  13. (1 – NDVI) simple ratio = ------------------------- (1 + NDVI) (1 – simple ratio) NDVI = ------------------------- (1 + simple ratio)

  14. If n is our friend, why is that N is our nemesis?

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