Corn planting dates, corn heights – 2013

“Knee high by the fourth of July!” Some of us grew up with that old saying which either foreshadowed disaster or forecast bumper yields. If corn was knee high by the fourth, most thought it would mature before the first fall frost. That was good news! The statement perhaps was valid back when the first target corn planting date was mid-May.

Farmers now begin planting in mid- to late- April and most wrap up planting by mid-May. Earlier planting occurs now due to many factors including: reduced tillage systems, better herbicides, more cold-tolerant hybrids, improved seed treatments, improved planter systems, larger farms, and climate change. And now, we’re used to seeing corn “…as high as an elephant’s eye, An’ it looks like its climbin’ clear up to the sky” (Rodgers and Hammerstein, 1943, musical, Oklahoma) by the fourth of July.

But that didn’t happen this year. Many agronomists report not only shorter corn plants than normal this year – at least in some parts of Iowa – but also more variability across what usually appear as uniform fields. Why? I’ll address this in two blogs. Let’s talk here about planting dates.

Remember when 2013 first rolled in, the impact and lingering effects of the 2012 drought still haunted us. Several articles ICM News articles reflected our concerns. By April 28 only 2% of Iowa’s corn lay in seed furrows, soaking up water, and bracing for up to several inches of snow. Then, after the snow, wet conditions stymied planting. By May 12th, only 15% of Iowa’s corn had been planted ( USDA data). A week later though, another 56% was planted! We planted about 1.5 million acres per field work day the week of May 13th – probably the most we’ve ever accomplished in one ‘field work day’ (Figure 1). We finally reached 99% of Iowa’s corn planted on July 1st. That ranks 2013 alongside 2008 in recent history; two of the slowest and most drawn out planting seasons of modern times.

But later planting dates usually result in taller corn than earlier planting dates since plants develop during periods with long days. Plant height increases because of elongated internodes during such days.

To see why we think corn is shorter this year, see my next blog posting as well as a complete article on the subject in the ICM News.

Certainly yield potentials are compromised this year due in part to late planting. We need a later than normal frost!

Figure 1. Corn planting progress in Iowa, 2004 and 2008 – 2013. Data compiled from USDA. The “blue bar” in the figure represents half (50%) of the acres planted. In 2010 (yellow) the crop was half planted April 18th, in 2013 the half planted date was about May 15th. The very high yield year of 2004 was 50% planted by April 30th.

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