Fontanelle
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Corn Adjusts to Late Planting Date
December 31, 1969
By Neal Borgmeyer
Fontanelle Regional Agronomist
In some parts of the Midwest, wet weather continues to delay planting. Producers in those areas may have questions regarding corn number choices. Research by Universities and also my personal experiences have shown that we can plant full season corn much later than was previously thought.
Corn adjusts to later planting dates
Researchers at Purdue University have studied the response of corn to early, mid and late planting dates. As the planting date was delayed, all corn numbers shortened the number of days from planting to silking thus reducing the time spent during vegetative growth.
Those corn numbers also increased the number of days between silking to black layer thus more time during grain fill. The change in the length of vegetative growth was greater than the time change during grain fill.
Corn adjusted to a shorter growing season by a reduction of 9 days total. For example a 115 RM corn planted on May 30th would thus behave like a 106 RM corn.
Area Corn Maturities Planting Date
Northeast Nebraska
Southern Minnesota 98 to 105 RM Up to May 27
Central Nebraska
Central and Northern Iowa
Central and Northern Illinois 103 to 110 RM End of May
Northern Missouri
Southeast Nebraska
Southern Illinois 111 to 115 RM End of May
Southern Iowa
Switching to Soybeans should not be considered until after June 15th in Iowa and Nebraska.
This decision should be based on the economic potential of both crops for a given planting date and should take into account the yield potential of both crops at that given planting date, as well as the expected market price of both crops.
If the normal yield potential is 200 bu/a for corn and 60 bu/a for soybeans, both crops planted on June 15th would yield about 68% of the yield potential for corn and 70% for soybeans (136 bu/a for corn and 42 bu/a for soybeans). Corn yields are then 3.2 times greater than soybeans yields, so soybean market price must be 3.2 times greater than corn or more in order to make soybeans more profitable to plant than corn. If corn price is $5.75 then beans would have to be $18.40.
For the Northern 1/2 of Missouri the late planted yield potential on June 15th for corn is 75% and 83% for soybeans, so this works out that beans need to be more than $17.25/bu to be more profitable to plant than corn.