How Warm Was it This Season?

Posted: September 29, 2015

You may recall we did not have an exceptionally early planting of our corn and soybeans this spring but our crops have matured early and are being harvested earlier than normal. How is that so?

According to the PA Weekly Weather Summary all of the reporting stations across the state are reporting above average Growing Degree Days (GDD) from April 1st-September 27th. The range is +156 to +1010 GDD, with many locations around +500.

So what is a GDD?  Without going into a lot of detail, it is the high and low temperature for a given day added together divided by two and subtracted from the base temperature. Corn and Soybeans grow between temperatures of 50 and 86 degrees. For more information on calculating GDD look at the Iowa State website.. Several smart phone apps are available for the searching to help with local determinations.

Typically when we talk about corn maturity it is in days not GDD, 95 day corn or 108 day corn. As you know the heat accumulated in a day in the spring or fall is not the same as a summer day. On average 20 GDD equals 1 day, so if we are 500 GDD ahead of average we are 25 days ahead of what would be considered normal for this time of year. That is why we harvesting corn with moisture in the teens in September even when it was planted maybe a week or so later than normal. Don’t forget, we also had a dry May and that allowed a great deal of corn and soybeans to be planted in a narrow window. To see the September 27th, 2015 issue of the NASS USDA PA Crop Progress and Condition report.

So why not take advantage of the early harvest and consider planting a small grain after your soybeans to provide winter cover and the opportunity to diversify your corn/soybean rotation.

Contact Information

Andrew Frankenfield
  • Extension Educator, Agronomy
Phone: 610-489-4315