Source: Chad Lee, Extension Agronomist, University of Kentucky

Corn planted later will germinate and emerge more quickly, and go through crop stages faster than corn planted early. Typically, corn requires about 100 growing degree days (GDDs) to emerge and about 200 GDDs to reach the V2 growth stage. An accumulation of about 475 GDDs is required to reach V6, the stage when the growing point moves above ground.

Typically, March accumulates about 170 GDDs, while April accumulates about 320 GDDs and May accumulates about 510 GDDs (Table 1). So far, the GDD accumulation for 2011 seems on track with the historical numbers (Table 2). Based on these long-term averages, corn planted the first of April will reach V6 early to mid May, corn planted the first week of May would reach V6 at the end of May or first of June and corn planted mid-May will likely reach V6 by mid-June.

The faster development from the later planting becomes very important for sidedress applications and timing of postemergence herbicides. Work that normally could be done four two five weeks after planting might need to be done three weeks after planting this year.

The faster development from later planting dates occurs through pollination and seed fill as well. Many corn hybrids require around 1200 to 1400 GDDs to reach pollination. Corn planted April 1 will reach pollination around mid-June while corn planted May 1 will reach pollination around the end of June or first week of July. So, a month delay in planting may only result in a two-week delay for pollination.

Table 1. Historical Corn Growing Degree Day Accumulations for Kentucky 1





































































Location

Mar

Apr

May

Jun

Jul

Accumulated Corn GDDs per Month 2
Mayfield
193

354

530

704

779
Paducah
162

324

529

721

828
Henderson
163

323

524

707

807
Hopkinsville
169

321

507

684

789
Bowling Green
168

313

515

692

805
Leitchfield
160

310

490

663

770
Somerset
172

306

474

639

743
Average
170

322

510

687

789
1 Data from Tom Priddy, UK Ag Weather Center.
2 Derived from 1961 to 1990 data.

Table 2. Corn Growing Degree Days accumulated in 2011.











































Location

GDDs accumulated for March, 2011

GDDs accumulated from April 1 to April 25, 2011
Cape Girardeau, MO
155

310
Mayfield, KY
178

352
Paducah, KY
168

350
Henderson, KY
152

320
Bowling Green, KY
192

352
Glasgow, KY
182

324
Somerset, KY
169

312
Bardstown, KY
165

303
Covington, KY
105

248

References:
NCH-40 Growing Season Characteristics and Requirements in the Corn Belt. National Corn Handbook.
University of Kentucky Ag Weather Center: http://wwwagwx.ca.uky.edu/