University of Minnesota Extension
/
612-624-1222
Menu Menu

Extension > Agriculture > Crops > Corn Production >Planting > What to do? 2013 growing season

What to do? 2013 growing season

By Ryan Miller, Extension Educator, Crops
June 2013

The weather has put us in a bind. About a third of the corn crop has been planted in Southeast Minnesota, which has led to questions on the "correct" course of action. There will be no one "correct" course of action and with fields unsuitable for planting and more rain in the forecast there will be no easy decisions. One choice could be to utilize prevented planting, a choice that is appropriate for some and will lead to many other decisions to be made. A second option is to switch corn acres to soybeans; this may also be a wise and appropriate decision for some acres. Remember when planting soybeans after June 10th it is generally recommended to drop 0.5 RM from your typical full season varieties. The final choice is to stay the course and plant corn, a perfectly viable option for some acres.

Remember corn needs heat to complete its life cycle and we have lost a month. The following figure is from the National Corn Handbook, it indicates how many Growing Degree Days 50/86 (GDD 50/86) it takes for different relative maturity corns to reach physiological maturity (when planted by May 1st).

Corn Relative Maturity GDD 50/86 to Reach Physiological Maturity
85-100 2100-2400
101-130 2400-2800

Similar information generated from commercial seed literature is as follows:

Corn Relative Maturity Approximate GDD 50/86 to Reach Physiological Maturity1

1 = Values are approximate and can vary from hybrid to hybrid within a relative maturity

78-79 1850
80-89 1900-2150
90-95 2150-2300
95-100 2300-2450

Late planted corn does not need as many GDD's to reach physiological maturity. In general there is a 6.8 GDD reduction per day for corn planted after May 1st. For corn planted June 1st that would mean a reduction of 210 GDD required to reach maturity. In other words a 100 RM corn hybrid planted in April takes about 2400 GDD to achieve physiological maturity. That same hybrid planted on June 1st would only take about 2190 GDD to reach maturity.

How much heat can we expect for the 2013 growing season? The following are a set of GDD 50/86 scenarios for different planting dates and locations in Southern Minnesota. Scenarios are based on the 1971 to 2000 temperature normal, information was derived from the Climatology Working Group (climate.umn.edu). October was excluded because there is about a 20% probability we will freeze before the end of September and about a 90% probability we will freeze before the mid of October. In addition we can only expect about 150 GDD 50/86 in October. Another cautionary note is that these scenarios are based on the 1971 to 2000 normal, and there is the possibility of accumulating more or less GDD's during the course of the summer (i.e. nothing is guaranteed).

GDD 50/86 Accumulation by Month
Location June July August September Total
Winona 551 685 620 376 2232
Rosemount 520 646 581 351 2098
Rochester 496 622 559 333 2010
Preston 504 632 570 344 2050
Owatonna 534 660 595 356 2145
N. Mankato 552 674 607 371 2204
Lamberton 565 672 599 359 2195
Worthington 520 646 570 336 2072
GDD 50/86 Accumulation by Month with 3 Weeks in June
Location 3 wks June July August September Total
Winona 423 685 620 376 2104
Rosemount 400 646 581 351 1978
Rochester 381 622 559 333 1895
Preston 388 632 570 344 1934
Owatonna 409 660 595 356 2020
N. Mankato 422 674 607 371 2074
Lamberton 432 672 599 359 2062
Worthington 400 646 570 336 1952
GDD 50/86 Accumulation by Month with 2 Weeks in June
Location 2 wks June July August September Total
Winona 298 685 620 376 1979
Rosemount 282 646 581 351 1860
Rochester 269 622 559 333 1783
Preston 274 632 570 344 1820
Owatonna 288 660 595 356 1899
N. Mankato 297 674 607 371 1949
Lamberton 303 672 599 359 1933
Worthington 282 646 570 336 1834
GDD 50/86 Accumulation by Month with 1 Week in June
Location 1 wk June July August September Total
Winona 164 685 620 376 1845
Rosemount 155 646 581 351 1733
Rochester 148 622 559 333 1662
Preston 151 632 570 344 1697
Owatonna 158 660 595 356 1769
N. Mankato 163 674 607 371 1815
Lamberton 165 672 599 359 1795
Worthington 155 646 570 336 1707

Bottom-line: as the season progresses we will accumulate less GDD's, and with the full month of June in a "normal" year we won't quite reach 2300 GDD 50/86. There is a good chance that if we plant corn with Relative Maturity of 95 or greater we will not reach physiological maturity. What to expect when we don't reach physiological maturity: lower test weights, excessive moisture, and the potential for harvestability issues. Harvestability issues will really depend on the amount of GDD's we accumulate, and the shorter we are on GDD's to reach physiological maturity the more issues we will have.

Shorter maturity hybrids, if available, will have less yield potential but will be more likely to reach physiological maturity. This means test weights should be better, but at this point in the season even short season hybrids will have significant moisture levels at harvest.

The scenarios are intended to give you a better assessment of risk for the relative maturities you intend to plant. Remember nothing is guaranteed.

  • © 2013 Regents of the University of Minnesota. All rights reserved.
  • The University of Minnesota is an equal opportunity educator and employer. Privacy