In a forthcoming issue of the Soil Science Society of America Journal, scientists at the University of Illinois at Urbana-Champaign will outline how current nitrogen recommendations are faulty, the soybean credit is invalid, and balanced fertility makes for optimum nitrogen uptake. As well, the article highlights the importance of plant populations and crop residue management for proper usage of nitrogen fertilizers.

"Our work involved 102 on-farm nitrogen-response studies conducted throughout Illinois in six growing seasons from 1990 to 2003. A site-by site evaluation of the proven-yield method showed that current fertilizer recommendations are not only wrong, they are scientifically indefensible," said Richard Mulvaney, a professor of soil fertility.

"We're on the edge of a revolution in nitrogen fertilizer recommendations," said Saeed Khan, a research specialist in agriculture and co-developer of the ISNT that estimates the soil's nitrogen-supplying capacity. "We're going away from yield-based management to a system that quantifies the main source, which is the soil,"

"The traditional 'proven-yield' approach says higher yielding areas need more fertilizer nitrogen, whereas crop nitrogen response is typically lowest in these areas. We have found that what matters most is how much nitrogen comes from the soil. Rich soils need less nitrogen from fertilizer, while poorer soils need more," Mulvaney said.

Balanced Fertility

Mulvaney and his colleagues looked at several sites where a high ISNT value was incorrect in predicting negligible response to applied nitrogen and concluded that balanced fertility is key to efficient crop use of fertili
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Contact: Gary Beaumont, Ag Communications
beaumont@uiuc.edu
217-333-9440
University of Illinois at Urbana-Champaign
1-Sep-2005