If weather permits, many corn producers will feel a strong desire to start planting very early. Fieldwork is advanced in some areas and March was dry, but memories of serious planting delays in 1993 are a major factor. It may be a very hard sell, but my best advice is to plan for a more normal spring in 1994. Switching from proven practices implies knowledge of what the unique weather conditions in 1994 will be, but the record for such assumptions isnt very good.
Many factors can influence the optimum date in a given year. For an additional discussion of this, see page 33 of the April 23, 1993 Integrated Crop Management newsletter. Long-term studies have pinpointed the late April-early May period as ideal in much of Iowa. It usually pays to have corn planting finished by May 10 to 15. The question of when to start is more difficult because it involves more than a date on the calendar. If I had to select the best date for a typical Iowa corn field, I would select the last week of April. Obviously, there are locations where and years when this may not be the case. For this discussion, the issue is how much earlier than the last week of April should planting start if conditions permit? The tactful answer is that depends.
The on what in this case includes yield expectations, soil conditions, and number of planting days needed. On average, yields for a week on either side of this period should not be greatly different, assuming soil conditions are desirable. The main issue is soil moisture. Is it too wet to have equipment in the field? Although Im not a big fan of using soil temperature to determine whether to plant the last week of April and not at all in May, it may be a factor to consider in early to mid-April. Do consider that soil temperature can fluctuate greatly. It may be 55F one day and 45F a week later, or vice versa.
But what if soil conditions are ideal relative to moisture and temperature? How much earlier than what I consider to be the ideal week do I start? I suggest that you consider the number of planting days needed. If you can plant the entire acreage in a couple of days, why not do it the last week of April? If it takes four or five days, it may make sense to start around April 20. In a normal spring, you can be in the field about half of the days. Those who need considerably more planting days may choose to start during the April 15 to 20 period in northern Iowa and April 10 to 15 period in southern Iowa. Earlier planting would work in many years, but the risk of uneven stands and possible replants seems greater than necessary.
If you start planting very early, the least risk would likely be with well-drained upland soils where the prior crop was soybeans. Also be sure seed quality is high. This is the place to use your full season hybrids. Whether or not very early planting is even possible will depend on weather prior to April 20. Certainly no one wants a repeat of the late planting of 1993, but there could be a tendency to overreact on the early side in 1994.