Published on Wednesday, April 29, 2015
Some areas throughout my geography began planting corn as early as April 1 - 6. Other notable planting windows have been April 10 - 17 and April 21 - 24. Soil texture and moisture have been desirable for field work in these areas, however, cold soil temperatures and rainfall forecasts have been a concern recently.
I have been asked several questions about the number of days required for corn emergence. Corn requires 110 - 120 GDUs (Growing Degree Units) from planting to emergence. I would recommend finding a weather data source that records daily high and low temps, or use Davis weather stations or something similar. I use www.weatherplot.com for this, but it is a subscription service. Also, a weather forecast site with a 10-day temp forecast would be helpful. I use The Weather Channel info on my iPhone for this.
To figure the GDUs of corn, take the Daily High Temp (50˚F or above, but not to exceed 86˚F) + Daily Low Temp (if low goes under 50˚F, then use 50˚F). Take that sum and divide by 2. Then, take this new number and subtract 50 from it. This will give you the GDUs for that day.
Let me illustrate this with an example below.
Assume: Corn was planted at 8 a.m. on April 15, 2015 at Downs, IL.
Weather data from www.weatherplot.com tells me the highs and lows for the following dates for that location are:
4/15: 72 high, 40 low* = 11 GDUs
(Ex. 72+50 = 122÷2= 61-50 = 11 GDUs)
4/16: 73 high, 53 low = 13 GDUs
4/17: 78 high, 50 low = 14 GDUs
4/18: 81 high, 56 low = 18.5 GDUs
4/19: 62 high, 54 low = 8 GDUs
4/20: 58 high, 43 low* = 4 GDUs
4/21: 60 high, 38 low* = 5 GDUs
4/22: 54 high, 35 low* = 2 GDUs
4/23: 60 high, 30 low* = 5 GDUs
4/24: 63 high, 40 low* = 6.5 GDUs
Total = 87 GDUs
*If the DLT is below 50˚F, remember to replace it with 50 in your equation.
From planting on 4/15 through 4/24, there have been a total of 87 GDUs accumulated at the Downs, IL location. This would tell you that the corn has not had enough heat units (GDUs) for emergence, and would still need about 28 GDUs. So now, you must look at the temperature forecast to predict when it will emerge.
Forecast 4/25: 57 high, 37 low = 3.5 GDUs
(Total of 90.5 GDUs)
Forecast 4/26: 61 high, 36 low = 5.5 GDUs
(Total of 96 GDUs)
Forecast 4/27: 63 high, 37 low = 6.5 GDUs
(Total of 102.5 GDUs)
Forecast 4/28: 66 high, 43 low = 8 GDUs
(Total of 110.5 GDUs)
Forecast 4/29: 68 high, 45 low = 9 GDUs
(Total of 119.5 GDUs)
This method would predict that corn planted on April 15, 2015 at Downs, IL would emerge on April 29, (plus or minus one day) with corn being in the ground 14 -15 days prior to emergence. Corn sitting in the ground for longer than 14 days is more susceptible to stand losses from seed decay, disease infection, attacks by insects, kernel rots, and crusted soil. Seed treatments are great protection, however, they are not bulletproof!
If you have a somewhat reliable 10 -14 day temperature forecast, you can even predict days to emergence for corn that has not been planted yet. I hope this helps explain the process and may be a simple refresher for many of you. Let me know if you have questions.
Have a great week!
Author: Chad Kalaher
Categories: NE Illinois, NW Indiana
Tags: Beck's Blog, AgTalk, Chad Kalaher, Agronomy, Agronomy Update, agronomist, Beck's Agronomist, indiana agronomy, Illinois agornomy, corn emergence, Illinois corn, Indiana corn
Beck’s Hybrids team sales agronomist for 22 counties in NE ¼ of IL and 7 counties in NW IN. Raised on grain and livestock farm in southern IL. B.S. Agronomy 1995 – University of Illinois, M.S. Weed Science 1997 – North Carolina State University. Previous positions in seed industry as researc
Beck’s Hybrids team sales agronomist for 22 counties in NE ¼ of IL and 7 counties in NW IN. Raised on grain and livestock farm in southern IL. B.S. Agronomy 1995 – University of Illinois, M.S. Weed Science 1997 – North Carolina State University. Previous positions in seed industry as research agronomist, district, and regional sales manager.
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