Figure 1. Percentage of South Dakota corn planted by week, 2018 versus the 5-year average.
Given the relatively late arrival of spring in South Dakota, many farmers are planting corn as soon as they are able to get in the field in an attempt to capture as many growing degree days (GGDs) as possible. Typically, by the first week in May, one-third of the corn is planted in South Dakota. In 2018, producers have only planted six percent. The USDA planting progress numbers through the first week of May for 2018 versus the 5-year average are shown in Figure 1.
The optimum planting window for corn in South Dakota ranges from late April to late May, varying slightly depending on the location within the state. Producers have been planting earlier in recent years, due in part to favorable early season weather, in an attempt to maximize yields. However, fourteen years of data from the Southeast Research Farm near Beresford, SD show that yield reductions typically do not begin until around May 20th for an early corn hybrid (101-103 RM) and around May 5th for a late corn hybrid (112-118 RM).
As a general rule, corn should be planted when 2” soil temperatures are 50°F or greater to ensure even germination. Even if the soil temperature remains above 50°F, it may take 20 days or more for emergence, depending on growing degree days. Soil temperatures below the mid-40s for several days are cause for concern.
Corn is particularly susceptible to low-temperature stress during germination, emergence, and the seedling stages. The inherent risks associated with planting in low soil temperatures include greater seed exposure to soil-borne diseases and insects, chilling injury and cold stress, delayed or uneven emergence, and the potential for frost damage later in the spring growing season. Corn is particularly sensitive to cold and wet soils during the imbibition period, which occurs as soon as the seed is exposed to moisture (usually immediately after planting).
Producers who have a large amount of ground to cover may accept these risks in order to finish in a ‘timely’ manner. Producers with fewer acres or a lower risk tolerance may be able to afford to wait for more favorable soil conditions and/or weather forecast.
Some management strategies for planting corn in low temperatures include:
- Consult your seed salesman or agronomist with advice on which hybrids may have better cold tolerance.
- Plant seed lots with good seed germination test ratings first.
- Plant well-drained soils with low residue cover first (these soils should be warmest).
Keep in mind that planting date in itself is not always the most important component of final grain yield. While it is nice to plant early and potentially capture more GDDs during the growing season, it is more important to plant when conditions are right.
- To Plant or Not to Plant Corn: A Moot Question?. By Robert Nielsen, Purdue University Extension Corn Specialist.
- Corn Requires Favorable Soil Temperature for Uniform Germination and Emergence. By George Silva, Michigan State University Extension Specialist
- Cold Temperatures and Corn Chilling Injury. By Nathan Mueller, Former SDSU Extension Agronomist.