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Illinois Soil Nitrogen Test Predicts Southeastern U.S. Corn Economic Optimum Nitrogen Rates

^a Dep. of Agribusiness, Science, and Technology Brigham Young Univ.-Idaho Rexburg, ID 83460-1100
^b Dep. of Soil Science Vernon James Research and Extension Center 207 Research Station Rd. Plymouth, NC 27692
^c Dep. of Soil Science North Carolina State Univ. Raleigh, NC 27695-7619
^d Dep. of Crop Science Vernon James Research and Extension Center 207 Research Station Rd. Plymouth, NC 27692
^e Dep. of Crop Science North Carolina State Univ. Raleigh, NC 27695-7620
^f Dep. of Soil Science North Carolina State Univ. Raleigh, NC 27695-7619

View larger version (27K): [in this window] [in a new window]   Fig. 1. Economic optimum N rate for the average fertilizer cost/corn price ratio (EONRavg) vs. the Illinois soil N test concentration (ISNTc) for all sites. Regression models were fit to the well and poorly drained sites.

View larger version (24K): [in this window] [in a new window]   Fig. 2. Humic matter (HM) vs. the Illinois soil N test concentration (ISNTc) for all sites. Regression models were fit to the well and poorly drained sites.

View larger version (54K): [in this window] [in a new window]   Fig. 3. Growing season (a) total precipitation and (b) mean temperature for 2001, 2002, 2003, 2004, and 30-yr average for the Lower Coastal Plain, Middle Coastal Plain, and Piedmont regions.

View larger version (28K): [in this window] [in a new window]   Fig. 4. Economic optimum N rate for the average fertilizer cost/corn price ratio (EONRavg) vs. the Illinois soil N test concentration (ISNTc) for 2003 and 2004 well-drained sites. Regression models are shown for 2003, 2004, and all well-drained sites in all years.

View larger version (26K): [in this window] [in a new window]   Fig. 5. Economic optimum N rate for the average fertilizer cost/corn price ratio (EONRavg) vs. the Illinois soil N test on a hectare furrow slice basis (ISNThfs) for well and poorly drained sites modeled using regression analysis.