Window of Opportunity

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, R2 = 0.53 • V10 to R1, R2 = 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) 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) 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 Yield effect is very weather-dependent!

24. 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