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13
Mar
2019
How Late Can I Plant Corn and Still Achieve Maximum Yields?
Author: Jason Kelley, Wheat and Feed Grains Extension Agronomist

By Jason Kelley, Wheat and Feed Grains Extension Agronomist

“How late can I plant corn” seems to be the topic on most corn growers mind lately as the wet weather pattern that started last summer has continued to keep tractors out of the field this winter.   Just how wet has it been in Arkansas?  From September 2018 through February 2019, the statewide precipitation ranking was the second wettest of all time for this 6 month period.  Many locations have received upwards of 40+ inches of precipitation during this time and as you might expect, little to no field work has been done and most fields are still rutted up from harvest last fall.   A tremendous amount of field work still needs to be done before corn can start planting corn.    

To date, no corn has been planted in Arkansas and it is doubtful that any will be planted in the next 10 days.  In some years we already have corn emerged by this date in south Arkansas, but certainly if conditions would allow for planting, planters would be running now in South Arkansas.  Considering the poor shape fields are in currently and the lack of field work to date, it seems like we are way behind on planting.  I have already heard some growers questioning whether they will be able to get their corn planted during the period when maximum yields can be achieved. What is the optimum planting date? Planting date studies suggest that corn has a wider planting window than most give it credit for, especially since most of the corn grown in Arkansas is irrigated.  Let’s look at the planting date information that has been collected in Arkansas and the mid-south over the last few years.      

Data from irrigated planting date studies conducted from 2008-2013 in Southeast (Rohwer), East-Central (Marianna), and Northeast Arkansas (Keiser) showed that on average 100% of maximum yield could be maintained with planting dates as late as April 25th in Southeast Arkansas and approximately April 30th in areas further north.  This goes against common thought that corn has to be planted as early as possible to get maximum yields and that planting date is not always the most important factor for yield.  

A six-year summary of % relative yield potential by planting date and location in the state (NE, EC, SE) is shown below.

Once corn yields started to decline, they slowly declined until Mid-May and then started to more rapidly decline through mid-late May at all locations.  

This data is in agreement with multi-year data generated from Dr. Erick Larson at Mississippi State University (http://www.mississippi-crops.com/2016/04/01/when-does-corn-yield-potential-begin-to-suffer-from-planting/) where he found that irrigated corn still produced optimum yields when planted as late as May 1 at Stoneville and Mississippi State University Campus locations.    

Early planting in some years can be of benefit, but our studies have shown that there is a broad planting window of approximately 6 weeks from Mid-March to Late April where yields are still maximized.   During the time of March-April when optimum yields should be realized, the goal should be to plant to achieve the best stand of corn possible and not consider the date as the most important factor for achieving high yields.  I would much rather wait a few days for soil conditions to improve to get an optimum stand than plant a few days earlier into a soil that is marginally too wet and have a poor stand that will hurt yield more than a few days of delay in planting.      

Since it looks like we will have only one opportunity to plant corn this year we have to make the most of it.  Focus should be on making sure that soil conditions are conducive for tillage and planting.  Avoid performing tillage on soils that are too wet which will likely lead to compaction and a cloddy seedbed, both of which will likely have season long negative effects on corn yield.   


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