Kentucky farmers are getting used to rising corn seed prices and that trend doesn’t seem to be coming to a halt anytime soon. Price increases can, in part, be attributed to various genetic technologies and seed treatments. In addition, farmers also are experiencing higher nitrogen prices. As a result, farmers are looking for ways to be cost efficient and still have high yielding cornfields.

The current seeding rate recommendation of corn grown for grain is a range of 22,000 to 30,000 seeds per acre. The lower number is targeted to less productive fields and the higher to more productive fields, said Chad Lee, Grain Crops Specialist with the University of Kentucky Cooperative Extension Service. For farmers producing corn for silage, Lee recommends 24,000 to 30,000 seeds per acre.

“Some farmers are pushing the upper limit by planting more than 30,000 seeds per acre,” he said. “The introduction of variable rate planters has brought forth the idea of targeting different populations across the field, based on prescription maps. Some of these farmers are varying nitrogen rates in addition to seed rates.”

Lee believes all these factors drive home the point that corn plant populations and nitrogen rates are ongoing questions.

A research study initiated in 2003 investigated various plant populations and nitrogen rates for both silage and grain yields. The first year of the project suggested that a population of 30,000 seeds per acre was as high as a corn population should go.

“In that study, corn was planted from 22,000 to 33,000 seeds per acre,” Lee said. “Silage yields were similar across all populations, and so were grain yields.”

Researchers applied nitrogen at a rate of 120 pounds of actual nitrogen per acre and 200 pounds of actual nitrogen per acre. Lee said the additional nitrogen did not increase silage or grain yields in most situations. The extra nitrogen did increase the yield of a leafy hybrid planted at the lowest seeding rates, but had no effect at higher seeding rates.

“There are a couple things to consider from the 2003 study,” Lee said. “For one, 2003 was one of the wettest years on record so water was not a limiting factor. This would also mean there was less competition among corn plants and that could have favored higher populations. On the other hand, the soil type was moderately productive soil in most years. The field produced yields over 200 bushels per acre, but 150 bushels per acre would be a typical year.”

Lee added that another factor was the location of the study.

“The study was conducted in the eastern half of Kentucky and may not correlate well to the western half of the state,” he said.

Current research still does not support higher plant populations or higher nitrogen rates, at least for the eastern half of the Commonwealth. Farmers who are watching their bottom line don’t need to buy excess seed or nitrogen when less will achieve the same results, Lee said.

“Plant populations in the range of 22,000 to 30,000 plants per acre are sufficient for excellent corn yields in the eastern half of Kentucky,” he said. “The current nitrogen recommendations for your soil type are still the best rates to follow.”

Lee stressed that the study was for one year only and he’s hesitant to make recommendations based on only one year of research. However, the current recommendations are based off of years of research and this research agrees with all previous research, he said.

For more information, visit the grain crops web site, or contact your local county Extension office.