Planting date trends
The fact that corn is now planted earlier than ever before is not a surprise to most. Many have discussed this and have known intuitively that it has happened. Let's take a look at the overall trends occurring in Iowa. We will use the 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 figure 1.
Figure 1: 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). [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 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 during 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 how early we can plant corn and still achieve optimum yields. Planting date data from two Iowa State University research and demonstration farms (see Corn planting dates) includes dates as early as mid- to late March. This data shows that yields were reduced at Nashua but not at Crawfordsville. Due to positive yield data like this, we expect to continue seeing earlier planting dates at least in some parts of Iowa in the future.
Portions of this text, written by Roger Elmore and Lori Abendroth, originally appeared in the Integrated Crop Management extension newsletter on pages 217-218 of the IC-496(22) - July 31, 2006 issue.
