CORN Newsletter: 2009-14, May 18, 2009

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C.O.R.N Newsletter 2009-14
May 18, 2009 - May 26, 2009

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Should seeding rates be changed for late corn plantings?
by Peter Thomison


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Past university research indicates that optimal plant populations for early (mid to late April) and late planted (late May to early June) corn are similar. Based on results of these studies, most extension agronomists recommend that final plant populations should not be changed as planting date is delayed. One of the questions I’ve been asked recently is whether seeding rates should be increased for late planted corn. I’m not aware of studies in the Corn Belt that show consistent yield benefits from increasing plant population in late plantings. If planting is delayed until early June, some Ohio data suggests that certain hybrids are more susceptible to stalk lodging at high populations. In a recent OSU study, effects of early (late April) and late (early to mid June planting dates) plantings on corn response to population (24, 30, 36, and 42000 plants/A) were investigated at three locations. Results suggested that final stands of 30,000 to 36,000/A were required for optimal yield for the late April plantings. However, for the early to mid June planting dates, the results indicated little benefit from increasing seeding rate and a significant yield loss at plant populations above 30,000 plants/A. For corn planted late, grain yields, averaged across the three locations, were 159, 161, 133, and 138 bu/A at 24, 30, 36, and 42, 000 plants/A, respectively. The lack of response to plant population was related to stalk lodging which ranged from 59% at 24,000 plants/A to 97% at 42,000 plants/A.

In delayed planting situations, use the optimal seeding rates for the yield potential of each field. Recommended seeding rates for early planting dates are often 10% higher than the desired harvest population. However, soil temperatures are usually warmer in late planted fields, and as a result germination and emergence should be more rapid and uniform. So, as planting is delayed, seeding rates may be lowered (decreased to 3to 5% higher than the desired harvest population) in anticipation of a higher percentage of seed emerging.

References
Nafziger, E.D. 1994. Corn planting date and plant population. J. Prod. Agric. 7:59-62.
Nielsen, R.L. and P.R. Thomison. 2002 .Late Planted Corn & Seeding Rates. OSU Crop Observation and Reporting Network Newsletter. May 13 - 20, 2002 C.O.R.N. 2002-13
http://corn.osu.edu/archive/2002/may/02-13.html [URL verified 5/15/08].

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C.O.R.N. is a summary of crop observations, related information, and appropriate recommendations for Ohio Crop Producers and Industry. C.O.R.N. is produced by the Ohio State University Extension Agronomy Team, State Specialists at The Ohio State University and Ohio Agricultural Research and Development Center. C.O.R.N. Questions are directed to State Specialists, Extension Associates, and Agents associated with Ohio State University Extension and the Ohio Agricultural Research and Development Center at The Ohio State University.

Information presented above and where trade names are used, they are supplied with the understanding that no discrimination is intended and no endorsement by Ohio State University Extension is implied. Although every attempt is made to produce information that is complete, timely, and accurate, the pesticide user bears responsibility of consulting the pesticide label and adhering to those directions.

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Issued in furtherance of Cooperative Extension work, Acts of May 8 and June 30, 1914, in cooperation with the U.S. Department of Agriculture, Keith L. Smith, Director, Ohio State University Extension.

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