Window of Opportunity Peter Scharf University of Missouri

Window of Opportunity? Sensors

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?

Effect of N timing on yield tassel

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

Effect of N timing on yield tassel

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

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

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

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

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

Prime window: V6 to V11? Discussion?

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

Effect of N timing on yield depends on placement…

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

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

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

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

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

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

Effect of N timing on yield tassel

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

Effect of N timing on yield Year # expts. Yield effect of sidedress Yield effect is very weather-dependent!

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

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