Is it Time to Plant Corn?

Corn planters are starting to roll in South Dakota. According to the April 25 USDA-NASS Crop Progress and Condition Report, 6% of the corn acres have been planted in South Dakota as of April 23, compared 13% and 7% for 2015 and the 5-year average, respectively. While some producers have been planting steadily for a week or more, others are waiting for a warmer weather forecast to begin.

Soil Temperature
Although temperatures for the week of April 24th-30th are forecast to be below normal, the extended outlook currently points to a return of more normal temperatures. As of April 24, vegetated soil temperatures at a depth of 2” ranged from the mid to upper 50’s throughout Eastern South Dakota. Soil temperatures for locations throughout the state can be found on the South Dakota Climate and Weather website.

There is no correct answer as to which calendar date a producer should begin to plant corn. Instead, producers should watch extended weather forecasts and monitor soil temperature. Corn should be planted into moist soils when 2” soil temperatures are 50° F or greater. If soil temperatures remain above 50° F, time from planting to emergence is around 115-120 growing degree days (GDDs). South Dakota typically receives about 10 GDDS per day during mid-late April resulting in a time to emergence of about 12 days. A stretch of below normal temperatures with only 5 GDDs per day would correspond to 24 days to emergence.

Risks
The inherent risks associated with early planting 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 season. Producers with 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.

Management Tips
Some management strategies for early corn planting include:

• Consulting your seed salesman or agronomist for advice on which hybrids may have better cold tolerance.
• Planting seed lots with good seed germination test ratings first.
• Planting 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 monitor soil temperatures and weather forecasts to plant when conditions are right.

Further Reading

• 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 South Dakota State University Extension Agronomist.

Source: Jonathan Kleinjan, South Dakota State University