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Early planted corn still a concernPosted Monday, May 16, 2011, at 3:34 PM
The corn crop's emergence and stand establishment has been a concern for many producers this year. Plants have been slow in emerging and stands have been erratic and in some cases thin and uneven. April was a wet and cool month. It takes about 155 growing degree days (GDD) for corn to emerge. We could expect any corn planted before April 13 or so to have emerged or to be emerging now. If fields are not emerging then you need to determine why and soon.
A lot of the symptoms that we are seeing can usually be associated with "chilling injury". This occurs when seeds take up water with temperatures in the 30s or low 40s. This causes physiological damage, with symptoms often including corkscrewing and proliferation of roots, including adventitious roots that arise from the mesocotyl very near the seed. Such seedlings often fail to emerge, either leafing out underground or using up reserves and dying before they find their way to the surface.
There is also an unevenness of emergence in some fields with some plants emerging while others remain up to an inch below the surface. This could be due to differences in soil temperatures and aeration, especially in lower areas. There could also be differences in seedling diseases and perhaps some insect injury. If the unevenness seems to be random down the row and seedlings appear to be healthy, this may result from small differences in temperature and perhaps in planting depth. The situation might be related to the presence of residue or to small differences in soil conditions, although a lot of this would not be expected. The cooler temperatures this year could be expected to magnify any small differences this year.
It is not possible to say whether the early-planted crop has suffered physiological damage that will limit its yield potential. When lower yields followed early planting, it was often when warm temperatures through V2 or V3 were followed by a stretch of cool weather at V3 or V4. A return to warm temperatures as occurred last week should do a lot to return these plants to normal, with little lingering effect on yield potential. The start of ear formation is still some weeks away, and if conditions are good then, maybe plants won't remember what they have been through. The low temperatures in April also mean that the growth advantage of early-planted corn will be less than normal. This means that corn planted the first half of May will not be as far behind corn planted the first half of April as would normally be expected.
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As our local University of Missouri Agronomy Extension Specialist, Crook has been writing a column for the print edition Agriculture page for the past three years and we will now be sharing it on our web version. Crook has a bachelor and masters degree in agronomy from University of Missouri and received his doctorate in Agronomy from Kansas State University. He was in soybean variety development research for 22 years for various seed companies and has been Saline County's agronomy specialist for 10 years.