Tuesday, November 14, 2006 - 8:45 AM
191-4

Using On-Farm Strip-Trials Across Many Sites and Years to Improve Nitrogen Management for Corn.

Gaylia Ostermeier1, Alfred M. Blackmer1, Antonio P. Mallarino1, Tracy M. Blackmer2, and Bradley Van De Woestyne3. (1) Iowa State Univ, 2209 Agronomy Hall, Ames, IA 50011, (2) Iowa Soybean Association, 4552 114th St, Urbandale, IA 503222, (3) John Deere, 4140 114th St, Urbandale, IA 50322

With the current trends of increasing N fertilizer cost and level corn grain prices, it is necessary for producers to apply rates of N that are economically justified.  Our objective was to use simple on-farm strip-trials to assess how yield responses and economic returns vary across many fields, years, and price ratios. We used a strip-trial methodology adapted to yield monitors, global positions systems, and geographical information systems to establish and harvest 200 strip-trials from 2000 to 2005 in Iowa.  The trials evaluated two N fertilizer rates differing by 56 kg N/ha that were replicated at least three times in each field. The lower N rate ranged from 48 to 172 kg N/ha across the trials.  We calculated yield responses from strip-means and calculated N returns to N using different fertilizer and grain prices. Results demonstrated the significant benefit of knowing the optimum N rate for each field within a range of 56 kg. Knowledge of field-specific N needs of corn and consideration of prices greatly improve the profitability of fertilization.

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