The fact that corn is now planted earlier than ever before is not a surprise to most of you. Many have discussed this and have known intuitively that it has happened. Although we are still in the middle of the growing season, let's take a step back and investigate overall trends occurring in Iowa. In this article, we look at National Agricultural Statistics Service data on corn planting progress over the last three decades to add some actual numbers to the discussion. By comparing when 50 percent of the corn crop has been planted, it is clear that planting has occurred steadily earlier as shown in the figure.

Iowa corn planting progress, 1975–2006. Compiled from National Agricultural Statistics Service data.

For example, 50 percent of Iowa's 2006 corn crop was planted by April 25. This is more than 2 weeks earlier than when 50 percent was planted during 1975-1979 (average was May 10). Iowa's 2006 corn crop was also planted earlier than in either of the two previous years (dates of 50 percent completion were April 30, 2004, and April 27, 2005 [individual data years are not shown in the figure]).

The 2006 planting season began at nearly the same time as in 2004 and 2005. Since 1990, producers have been starting to plant at approximately the same time, except for the five-year window of 1995-1999, which was delayed. Producers are starting earlier and finishing sooner, yet the total time required for planting has changed little over time. On average, planting takes from 6 to 8 weeks to complete. The exception occurred between 1990 and 1994, when 10 weeks were needed to plant the crop.

Numerous factors enable fewer producers to get over their acreage earlier than ever before, while still only taking 6 to 8 weeks overall to plant. Wider planters coupled with more cold-stress tolerant hybrids, improved seed treatments, and reduced tillage systems have each contributed to this change. As producers farm more acreage, they must naturally start earlier if they want the majority of their corn planted around the optimum planting window for their region. This is based on the fact that producers face a larger yield reduction by planting too late rather than too early.

The trend to earlier corn planting in Iowa does not appear to be slowing.

One wonders, though, how early we can plant corn and still achieve optimum yields. Recent planting date data from two Iowa State University research and demonstration farms were presented in the March 13, 2006, issue of ICM Newsletter, (pages 61-62). Planting dates as early as mid- to late March were included. Yield potential was reduced at Nashua but not at Crawfordsville.

Due to positive yield data like this, we expect to see earlier planting dates at least in some parts of Iowa in the future.