With lower soil temperatures still persistent in parts of northern states, and many growers ready to plant, it’s important to understand the impact soil temperatures can have on corn emergence. It is recommended that farmers plant when soil temperatures are at or above 50 degrees F because lower temperatures can affect corn emergence and seedling health, which result in stand loss.
The impact of low soil temperatures ranges from abnormalities such as corkscrews or fused coleoptiles to seed death, according to Pioneer Seeds. Fields with residue tend to hold excess water and significantly lower soil temperature in the spring, promoting seedling disease, particularly in fields that are not well drained or have a history of seedling blight. The chances of establishing a good stand are greatly improved if seeds are able to germinate at least one day in warmer, moist conditions before a cold-stress event.
A square bottom spade is a simple, but effective tool for diagnosing emergence issues. By breaking the soil cleanly, the spade preserves the soil structure around the seedling, revealing any emergence issues that may have occurred.
“This method allows us to discover many things about the emergence process,” said Gary Brinkman, Pioneer Field Agronomist. “You can determine whether your seeds are planted deep enough or if you planted too early and into cold soils. This process lets us see the cold injury symptoms up close.”
Sidewall compaction, root decay and seed rot are just a few issues growers should look for when performing this test. To help reduce genetic vulnerability to stand loss from low soil temperatures, Brinkman recommends selecting hybrids with high stress emergence scores. Brinkman explains the process in the video below.
Delayed emergence due to cold, wet conditions lengthens the duration during which seed and seedlings are most vulnerable to early season insects and diseases. However, check out this article to avoid early-season stress on plants.