Ideally, soil temperatures, measured at seeding depth taken at 8 a.m. should be 50 degrees or greater.

By Jeff Burbrink
Extension Educator, Purdue Extension Elkhart County

Jeff Burbrink
Extension Educator, Purdue University Elkhart County

GOSHEN — We have all heard it repeatedly. Research has shown that early planting time, both for corn and soybeans, can lead to higher yields by the end of the season. That’s a fact that I think gets taken out of context.

That research is true if you hold all other factors equal. Things like cold and wet conditions probably have a greater impact on the health and yield of the crops than a date on the calendar.

I learned that lesson early. Dad always said that soil conditions, not the day on the calendar, are what should drive planting. I remember him pointing out one fella down the road who always was first to plant. That field was almost always the worst-looking field in the neighborhood.

Planting in poor conditions in order to not lose yield based on an ideal planting date may result in uneven stands which may also hurt yields. When it comes to deciding to plant, you should ideally look for warm soils that are not overly moist and plant approximately 10 to 14 days before the average date of the last killing frost.

Around Goshen, that is the last week of April. Based on our current wet conditions, it looks like most of the county will be planted after that date.

Soil temperature is still one of the most important factors in determining when corn can be planted. Ideally, soil temperatures, measured at seeding depth taken at 8 a.m. should be 50° F or greater.

In addition, the weather outlook for the following 5 days should indicate warm conditions. Planting before cool, rainy conditions may result in poor emergence due to chilling injury or by seeds imbibing cold water, with “corkscrewing” of the germinating plant being a sign of such conditions.

And there is good research from Indiana and Ohio showing that a hybrid planted 30 days late can reduce the necessary growing degree days to reach the black layer by 6.8 degrees per day of late planting. This suggests that a hybrid that takes 2600 growing degree days (GDDs) to mature can do so with 200 fewer GDDs when planted 30 days late.

However, late-planted full-season hybrids may take longer to dry down than a shorter season hybrid planted on the same date. While many hybrids are much better adapted to handle cold and wet soils than they were 50 years ago, sitting in the cold, wet soil for the sake of early planting often is not productive.