1. Improving NUE in Corn With Crop Sensing: Reflections, Concerns, and Needed Research Rain 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 3.612.8

11. Profile inorganic N related to EONR for 2004 fields 3.612.8

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 Vis simple ratio = --------------- NIR NIR- VIS NDVI = -------------------- NIR +VIS

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

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