Spring planting season has arrived and with it comes the need for farmers to take a look at the yield potential of their fields to determine corn seeding rates, said Ohio State Extension agronomist Peter Thomison.

"Newer hybrids are more stable under stress with improved resistance to lodging, diseases and insect pests," Thomison said. "Our studies have demonstrated that the superiority of modern hybrids is fully expressed only at a higher plant population. Most corn agronomists recommend adjusting seeding rates by using the yield potential of a site as a major criterion for determining appropriate plant populations."

Some seed companies recommend final hybrid stands as high as 36,000 plants per acre.

According to the USDA's National Agricultural Statistics Service, Ohio corn populations have increased by 16 percent over the last 10 years.

Final corn stands in Ohio in 2009 averaged 28,200 plants per acre and nearly a third of the state's corn acreage was 30,000 plants per acre or higher. Just three years ago, final stands averaged 30,000 plants per acre on only 14 percent of the corn acreage.

In 2006, Thomison and his colleagues initiated a study of corn response to plant population across a range of production environments. Tests were conducted at eight to nine locations annually in fields with high yield potentials of 200 or more bushels per acre. Results have varied over the past four years with yields averaging anywhere from 177 bushels per acre to 228 bushels per acre.

"In 2006 and 2009 results suggested that final stands of 36,000 per acre were required for optimal yields," Thomison said. "However, in 2007 and 2008 there was no yield response to plant populations above 30,000 plants per acre.

"Higher plant populations usually were associated with more stalk lodging, as well, with the most severe lodging occurring in 2008 as a result of high winds from Hurricane Ike. The extensive stalk damage may account in part for the absence of yield increases above 30,000 plants per acre."

Based on OSU studies to date, Thomison said a seeding rate of 31,000-33,000 seeds per acre will be adequate for optimum yields in most production environments in late April and early May. However, for fields with low yield potential, seeding rates of 24,000-26,000 seeds per acre should be sufficient.

By the same token, Thomison said fields with very productive soils and high yield potential, seeding rates of 36,000-37,000 seeds per acre may be necessary.

"Planting rate or population can be cut to lower seed costs, but this approach typically costs more than it saves," he said. "Most research suggests that planting a hybrid at suboptimal seeding rates is usually more likely to cause yield loss than planting recommended rates. It's best to follow seed company recommendations to adjust the population for specific hybrids."

SOURCE: Ohio State University.