Corn Illustrated: Early Harvest Indicates Typical Nitrogen Pattern

Very low yields, but trends hold true.

The Corn Illustrated nitrogen study is completed; or at least the corn is out of the field. There are still numbers to crunch, correct for moisture and then analyze. But some patterns appear evident just from the raw data. The plot was harvested on Friday, Sept. 7 at Jim Facemire's farm near Edinburgh, Ind.

Severe drought affected the plots. The soil there consists of three feet of loam topsoil over gravel. The corn showed good yield potential until around July 30. Then within 10 days, leaves turned brown, plants shut down and ears went from milk to brown layer stage, which precedes black layer, or full maturation after which point rain won't help. It didn't matter- less than half an inch fell in August anyway. Finally, the plot area received 1.3 inches a week ago, after the nitrogen plot was already harvested! Facemire reports less than 5 inches of rain from May 1, planting date, to harvest, in more than 30 rain events, with the biggest being a 1.1 inch rain in late June. That's not a recipe for growing corn!

"This year is still valuable in terms of learning about nitrogen response and how hybrids perform under stress," says Dave Nanda, president of Bird Hybrids, LLC, Tiffin, Ohio and consultant for the Corn Illustrated project. "It's very bad for farmers, but from a researcher's standpoint, it puts in the low end- that year of extreme stress. Now we need to see reactions under more normal and even good years, when rainfall is plentiful."

The '06 season was near the ideal side in the plot area. Nitrogen comparison plots with a different sponsor, Stewart Seeds, Greensburg, Ind., in small plot format a year ago yielded double or more at nearly every nitrogen level. Yields were compressed this time, but the trend was still there.

"Obviously you can't grow corn without N," Nanda says. Yields will likely wind up in the 30 to 40 bushel range when corrected in the zero nitrogen plots. This field-size plot was replicated, with two hybrids in each of two replications.

The surprise this year was a missing link last year. That was the 50 pounds of N per acre rate. Counting N applied before planting as broadcast, the actual rate was closer to 60 pounds per acre. This field also followed soybeans. The weigh wagon scales indicated that the 50 pound rate, while in between zero and 100 pounds per acre, leaned toward the 100 pound side.

Last year, under nearly ideal weather conditions as far as rainfall amount and timing, plus much cooler temperatures overall during the summer, yield topped out at about 100 pounds of sidedress N per acre, or about 120 pounds per acre, not counting any N contribution from soybeans, believed to be about 30 pounds per acre. The 50-pound rate was not included last year. Top yields in the plot this year will approach 90 bushels per acre.

This year, unofficial data leans toward response continuing until 150 pounds per acre. While somewhat erratic, yields leveled off at 200 and 250 pounds per acre. Other effects thought to be associated with higher N rates, such as higher moisture levels, seemed to hold true, although all moisture levels were low for harvesting mid to full-season hybrids during the first week of September. Moisture content coming off the combine into the weigh wagon ran from about 12% to a high just over 17%. The highest reading came from a high-N plot.

Stay tuned for more specific details, and watch your November and February issues of Midwest Farm Progress magazines for more observations from the plots.

TAGS: Soybean
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