March 22, 2013

This is from a posting by Jennifer Rees on JenREESources's Extension Blog.

Even with recent rain and snow events, the subsoil is still dry and farmers may be asking whether they should adjust their corn planting rates for 2013. A look at on-farm archive/-/asset_publisher/VHeSpfv0Agju/content/research conducted by Nebraska growers from 2010 to 2012 offers some answers. These growers were among the many who have participated in the Nebraska On-Farm Research Network, a project sponsored by UNL Extension in partnership with the Nebraska Corn Growers and the Nebraska Corn Board. Through it farmers work with Extension educators and specialists to design archive/-/asset_publisher/VHeSpfv0Agju/content/research they can conduct on their farms to answer their crop production questions.

From 2010 to 2012 a group of farmers conducted on-farm archive/-/asset_publisher/VHeSpfv0Agju/content/research to look at corn population rates in both rainfed and irrigated fields. They followed one of three planting rate protocols:

• 28K, 32K, 36K, 40K (40,000 seeds/acre) or
• 30K, 34K, 38K, 42K for irrigated production and 18K, 22K, 26K, and 30K for dryland production.

Their archive/-/asset_publisher/VHeSpfv0Agju/content/research findings showed that each hybrid varies in its response to increasing populations; however, with newer hybrids, there was a general trend that increasing population resulted in increased yields (see 2012 results below). Dr. Tom Hoegemeyer, UNL Agronomy Professor of Practice, attributes some of this to improved genetics that help hybrids combat stresses while maintaining yields.

Contact your seed company to learn the recommended planting rates for your hybrids. In determining the population calibration curve for each hybrid, many seed companies have developed recommended planting rates that can help guide the planting rates you use for your conditions.

Even with this data, you may question whether their recommendation is truly the best population for your field. On-farm archive/-/asset_publisher/VHeSpfv0Agju/content/research can help answer that. We recommend testing the recommended population against a higher and lower population with at least 4000 seeds/acre difference in planted population, regardless of whether it’s irrigated or dryland.

Corn Population Recommendations

In most of our irrigated studies, economically, many hybrids maximized yields and economic returns between 32,000 and 36,000 seeds/acre. This is very hybrid specific, which is why I recommend visiting with your dealer and conducting your own test.

In limited irrigation situations, UNL archive/-/asset_publisher/VHeSpfv0Agju/content/research has shown yield losses by backing off populations too far in a dry year. (See CropWatch stories, Corn Populations and Deficit Irrigation and Is a Population Change Warranted in Irrigated Corn Due to Water Constraints?) In dryland in eastern Nebraska Dr. Hoegemeyer's recommendation is that most hybrids, even when planting in soils with a low soil moisture profile, be planted at 24,000-28,000 seeds per acre.

While we don’t have moisture in our profile now, the potential for rain from March to May is usually pretty good. Planting a reduced population can short-change yield if precipitation develops.

In dryland in central to western Nebraska, populations of 20,000-22,000 seeds/acre will work for many hybrids. Crop genetics have made big strides since the last drought in 2007 when we were planting 18,000 seeds/acre in dryland. (See compiled results of dryland and irrigated on-farm archive/-/asset_publisher/VHeSpfv0Agju/content/research corn population trials from 2010 to 2012.)

If you’re interested in conducting seeding rate trials, please contact anyone on the UNL On-Farm Research Team. All our studies are posted on the CropWatch On-farm Research page.

Jenny Rees, Extension Educator
Tom Hoegemeyer, Agronomy Assistant Professor of Practice
Keith Glewen, Extension Educator
Gary Zoubek, Extension Educator
Steve Spicka, Extension On-Farm Research Technician
On behalf of the On-Farm Research Team