1. Window of Opportunity Peter Scharf University of Missouri

2. Window of Opportunity? Sensors

3. Factors defining the window  Effect of N timing on yield How late can you go?  Effect of sensor timing on diagnostic accuracy How early can you go?

4. Effect of N timing on yield tassel

5. How late can you apply?  Planned single application: as late as V11? Northern data needed

6. Effect of N timing on yield tassel

7. How late can you apply?  Planned single application: as late as V11? Northern data needed  With modest preplant N: later yet

8. How late can you apply?  Planned single application: as late as V11? Northern data needed  With modest preplant N: later yet  As a rescue application: at least silking

9. Factors defining the window  Effect of N timing on yield  Effect of sensor timing on diagnostic accuracy

10. Effect of sensor timing on accuracy  Can work as early as V6

11. Effect of sensor timing on accuracy  Chlorophyll meter prediction of N rate V5 to V9, R 2 = 0.53 V10 to R1, R 2 = 0.66  Chlorophyll meter: equation changes as season progresses

12. Prime window: V6 to V11? Discussion?

13. Effect of N timing on yield  Russelle et al. 1983  Evanylo 1991  Jokela and Randall 1989  Sripada et al. 2005  Miller et al. 1975  Hoeft  Bausch

14. Effect of N timing on yield depends on placement…

15. …and source (N burn) (average of 7 locations in Missouri, 2003-04) Treatment 1 foot 2 feet 3 feet 4 feet Ammonium nitrate 182018 28% N solution 9143361 Urea00X4 Yield loss (between-row minus broadcast) when 150 lb N applied broadcast at corn height:

16.  Kansas producer 2006: 4000 acres of corn fertilized in six days using sensors

17. …and source (N burn) (average of 7 locations in Missouri, 2003-04) Treatment 1 foot 2 feet 3 feet 4 feet Ammonium nitrate 182018 28% N solution 9143361 Urea00X4 Yield loss (between-row minus broadcast) when 150 lb N applied broadcast at corn height:

18. Effect of N timing on yield tassel Scharf et al., 2002, Agron. J. 94:435-441

19. Effect of N timing on yield tassel Binder et al., 2000, Agron. J. 92:1228-1236

20. Effect of N timing on yield tassel Walsh, 2006, MS Thesis

21. Effect of N timing on yield tassel

22. Effect of N timing on yield  Producer N rate, preplant vs sidedress (on average V9)  Field-length strips

23. Effect of N timing on yield Year # expts. Yield effect of sidedress 20047-5 20055-16 20065+4 Yield effect is very weather-dependent!

24. Only when corn has visible N stress Yield response to late N: Only when corn has visible N stress

25. Window of Opportunity: Later for unplanned (rescue) applications  Application until at least silking can give a large yield response when N stress is substantial  35 to 50 bu/ac in three MO tests