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Determining best planting date

We’ve experienced another abnormal planting season in Iowa, but all is not lost with later-than-normal corn planting dates in 2011. This proves again that our conditions are not always better than average — contrary to all the children of Lake Wobegone. After all, averages saunter near the midpoint of an extensive range of possible outcomes.

Let’s think about planting decisions while 2011 memories are still fresh:

Scenario 1. Assume it’s the second week in April. Soil temperatures at 4 inches have reached the low 50s, far above normal; air temperatures climb into the 80s; the soil is perfect for planting. Your seed is delivered and awaits in neatly stacked columns on pallets, organized and ready to go. Your planter poised, greased and precisely adjusted; the tractor fueled, with the oil changed; and the five- to seven-day forecast calls for warmer and drier conditions. Would you plant corn? Should you?

You know that most research data demonstrates that planting between mid-April and early May optimizes yields. Plus, you know smaller yield penalties occur for early planting than for late planting. Many farmers would start planting.

Scenario 2. What if all other factors matched those of Scenario 1, but weather forecasters call for colder and wetter conditions within a week instead of warmer and drier? Some areas may actually receive snow! Would you plant? Should you?

This second situation should force us to reconsider our choices and puts us in a dilemma. Should we put 35,000 precious seeds per acre at risk in an environment that may turn inhospitable before the seed has a chance to emerge?

When I pose these contrasting scenarios in winter meetings, most farmers respond quietly to the second situation, ”No, I’d wait.” But invariably some respond adamantly with “I’d plant!”

Scenario 2 shows up this year

Although poised here as hypothetical, we did indeed experience the second scenario in Iowa this year, the second week in April. The result: Only 2% — perhaps 275,000 acres -— of Iowa’s corn lay in the soil by April 17. Those who planted early did so for plausible reasons perhaps related to the number of acres they must plant, a need to check the planting system out or various personal considerations.

After that initial week, little corn planting progress occurred until the first week in May when it warmed up and dried off. Our progress in April matched the 1975-79 average. Does the “late” 2011 planting doom the crop to mediocre yields?

First, consider that Iowa’s planting progress the first week in May was spectacular; farmers planted 61% of our corn that week! In terms of percentages, that is next best to that of the first week in May 1992, when 64% of the crop was planted. Iowa ended up with 13.2 million acres of corn in 1992; we planted 8.45 million acres that week alone. According to USDA records, all seven days of that week in 1992 were suitable for fieldwork.

In comparison, this year we expect to have 13.9 million acres; that means we planted 8.48 million acres the first week in May. If you consider we had 6.2 days suitable for fieldwork, we planted 1.37 million acres of corn per day. That daily planting rate compares with what occurred the week ending April 25, 2010, when we planted 1.4 million acres per day for the 4.7 days suitable for fieldwork that week. We can plant corn quickly in Iowa!

The rapid pace the first week of May this year brought our planting progress up to that of the 2005-09 average. At the time I’m writing this, the rate of planting since early May pushed us to reach within 3% of the amount planted last year at this time, which was a record in itself.

The ‘best’ planting date

Of course, we won’t know the best planting date for 2011 until we summarize this year’s harvest data. Is it better to push planting early by mudding in corn, or is it best to wait until conditions improve? We learned in 2008 that the best planting dates were not necessarily the earliest at all locations. In most situations, it doesn’t pay to plant corn in marginal conditions. Plant-to-plant variability increases and yield potential decreases.

We may not have lost any corn yield potential as a result of our extraordinary 2011 planting season — extraordinary is another word for abnormal. Although we know the importance of planting date, the conditions at planting and those that immediately follow are even more important.

The remaining growing season will strongly influence final yields. We did our best with planting Iowa’s 2011 corn crop, and it may prove to maximize yields.

Visit for more corn management information.

Elmore is the Iowa State University Extension corn agronomist.

This article published in the June, 2011 edition of WALLACES FARMER.

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