By TIM ALEXANDER
Illinois Correspondent

BLOOMINGTON, Ill. — Achieving greater plant populations by applying higher input levels is seldom a guarantee of higher corn yield returns, according to Emerson D. Nafziger, professor and extension agronomist for the University of Illinois Department of Crop Sciences.

“In fact, (the trend of applying higher levels of nitrogen, phosphorous and potassium to crops) is a little bit troubling to me, to be honest,” Nafziger told 175 farmers and agribusiness representatives gathered in Bloomington on Jan. 10 for the 14th annual UoI Corn & Soybean Classic.

“Do high inputs equal high yields? Many say you can’t expect to get high yields without high inputs. But can we guess when that will or won’t happen so we can manage better? How routine can we be in putting on heavier inputs?”

According to Nafziger, tests conducted by the UoI have proven yield results are inconsistent when applying “heavy” amounts of plant nutrients compared to “normal” amounts. Therefore, the consistency indicates that applying a formula which includes increased levels of many inputs may not prove to be an effective strategy for raising returns in most environments. He said that taking control of one’s growing environment through irrigation or other practices, however, allows for more consistency in corn’s response to increased levels of some inputs.

Adding high input levels to a field averaging 150 bushels per acre will result in either no yield increase or increases too small to justify the added expense in most cases, Nafziger reported.

“We probably have gotten ourselves a little bit overconfident in what we are doing in terms of management,” he said. “Basically, these inputs by themselves aren’t going to help you.”

The effect of normal and high levels of tillage (normal: fall chisel; high: deeper or more thorough tillage), fertilizer (normal: 220 pounds of N plus normal levels of P and K; high; 320 pounds of N plus additional P and K)) and plant population (normal: 32,000; high 40,000) on continuous corn have been tested by the UoI for seven or eight years in productive soils at university crop science research centers in central and northern Illinois, where corn-on-corn is more prevalent.
The research revealed that over 16 site-years, yields were around four bushels per acre higher with deeper or more thorough tillage. UoI agronomists are noncommittal as to the contributing factors to the increase in yields, and remain unsure whether increased inputs could be credited, according to Nafziger.

Even when growing conditions were conducive to high yields, additional inputs could not be conclusively credited with increasing plant populations and producers’ profits, the UoI’s research concluded.

Further, Nafziger announced, adding insecticidal (Bt) and herbicide resistance traits to genetically modified corn hybrids has not been proven through the university’s research to enhance yield potential, though their inclusion undoubtedly protects crops from insect pests.

For a detailed summary of Nafziger’s presentation, contact him via e-mail at ednaf@illinois.edu