April in MFA's trade territory gets farmers thinking about corn planting. If weather permits, corn will be planted despite calendar date or soil temperature. The optimum time to plant corn usually occurs between late April and mid-May in the Midwest. I discussed early corn planting in 1995 and feel it is time to review it again.

During the past few field seasons, we have seen a tremendous increase in very early (early April) corn planting across the Midwest. Generally, these early plantings have been done against the "expert" advice of people such as myself. However, for the most part, the early planted corn yielded better than its "optimum-planted" counterparts during the past few years. It has been suggested the modern hybrids have better seedling vigor and can withstand cooler environments than their predecessors. This may be true. However, I believe the warmer weather and drier springs are the reason early planted cornfields have performed better than expected. Judging from this winter, I do not believe this "warming trend" has become the norm.

My main reason for concern with early planting is that I despise replanting. The toughest field visits I make concern replant decisions resulting from poor stand establishment. Time delays, costs involved, lack of residual weed control, poor pre-plant nitrogen use efficiency and duplication of effort all make replanting undesirable. The two most common causes of reduced stands are 1) planting too early--especially into cool/wet soils and 2) planting at improper seeding depths.

Seeding depth interacts strongly with planting date. Corn seedlings emerge as a single seed leaf (monocot), which can push through several inches of soil if necessary. Regardless of seeding depth (below 1 inch), the corn-growing point, nodal system and secondary-root system will be initiated approximately one inch below the soil surface. Planting corn shallower than one inch will result in placing the growing point near the soil surface, which may cause freeze damage or poor root establishment, especially on early planted corn. Corn can extend the region from the seed to the growing point several inches when planted deep. However, this elongated region increases the chance of disease or insect damage. This potential damage is especially prevalent in early planted corn, which may not be growing adequately enough to "outgrow" these problems because of a cooler environment.

For faster germination and better seedling vigor at early planting dates, shallow seeding (1 to 1.5 inches) takes advantage of more favorable soil temperatures near the soil surface. However, soil near the surface cools down faster in the evening and can result in poor germination or seedling injury if cold temperatures occur. At late planting dates, soil temperatures are adequate at all planting depths, and soil-moisture content becomes the limiting factor for rapid, early season growth.

Research at the University of Missouri by Dr. Bill Wiebold has shown no yield reduction with delayed corn planting through at least mid-May. The minimum optimum soil temperatures for corn planting should be at least 50 to 55 degrees F. Those who plant corn before the soil reaches this temperature range risk poor emergence and often have to replant, especially under wet soil conditions.

Obviously, I am not a strong proponent of early planted corn. Do not plant crops solely based on calendar date. Select planting dates based on soil temperature, local weather conditions and the extended weather forecast. Always take soil-temperature readings in the early morning to obtain the coolest environment that planted seed will be exposed to. If you decide to plant corn early, consider the following advice:

1. Plant full-season varieties.
2. Plant seed at the shallow end of the optimum-depth range for your field environment.
3. Be especially cautious when planting early in no-till or reduced-tillage systems because they tend to remain cool and wet.
4. Consider using starter fertilizer to overcome limited root growth and nutrient uptake.
5. Increase seeding rates 10 to 20 percent to compensate for early season induced stand reduction.
6. Plant first on well-drained fields with a southern- or southwest-facing slope.
7. Go fishing for a few days until the feeling passes.