By Peter Thomison, Corn Cropping Systems Extension Specialist; Steve Culman, State Specialist in Soil Fertility

As of Sunday, May 8, 30% of Ohio’s corn crop was planted, which is 14% behind last year and 5% behind the 5-year average. Weather forecasts indicate more rain this week, possibly continuing through Thursday. As prospects for a timely start to spring planting diminish, especially in northern Ohio, growers need to reassess their planting strategies and consider adjustments. Since delayed planting reduces the yield potential of corn, the foremost attention should be given to management practices that will expedite crop establishment. The following are some suggestions and guidelines to consider in dealing with a late planting season.

Although the penalty for late planting is important, care should be taken to avoid planting operations when soil is wet. Yield reductions resulting from "mudding the seed in" are usually much greater than those resulting from a slight planting delay. Yields may be reduced somewhat this year due to delayed planting, but effects of soil compaction can reduce yield for several years to come. (Keep in mind that we typically don’t see significant yield reductions due to late planting until mid-May or even later in some years.)

If you originally planned to apply nitrogen (N) pre-plant, consider alternatives so that planting is not further delayed when favorable planting conditions occur. Although application of anhydrous N is usually recommended prior to April 15 in order to minimize potential injury to emerging corn, anhydrous N may be applied as close as a week before planting (unless hot, dry weather is predicted). In late planting seasons associated with wet cool soil conditions, growers should consider side-dressing anhydrous N (or UAN liquid solutions) and applying a minimum of 30 pounds N broadcast or banded to stimulate early seedling growth. These approaches will allow greater time for planting. 

Similarly, crop requirements for phosphorus (P) and potassium (K) can often be met with starter applications placed in bands 2 inches to the side and 2 inches below the seed. Application of P and K is only necessary with the starter if they are deficient in the soil, and the greatest probability of yield response from P and K starter is in a no-till situation.  Remember, the longer our planting is delayed, the less beneficial a starter with P and K will be, because later planting dates typically have higher soil temperatures.

Don't worry about switching hybrid maturities unless planting is delayed to late May. If planting is possible before May 20, plant full-season hybrids first to allow them to exploit the growing season more fully. Research in Ohio and other Corn Belt states generally indicates that earlier maturity hybrids lose less yield potential with late plantings than the later maturing, full-season hybrids.

In delayed planting situations, use the optimal seeding rates for the yield potential of each field. Recommended seeding rates for early planting dates are often 5-10% higher than the desired harvest population because of the potential for greater seedling mortality. However, soil temperatures are usually warmer in late planted fields, and as a result germination and emergence should be more rapid and uniform. So as planting is delayed, seeding rates may be lowered (decreased to 3% higher than the desired harvest population) in anticipation of a higher percentage of seedlings emerging.