Assessing available N from fall and spring applications
Sidedress N application rates
If no fertilizer N has been applied this season or soil N measurements suggest little N remains from fall- and spring-applied N, consider using our current N rate recommendations based on results of field trials conducted since 2006 throughout the state using efficient methods and timings of N fertilizer application. The estimated Agronomic Optimum N Rate (AONR) for fine textured soils in westcentral and northwest Indiana is about 173 lbs N / ac. The AONR for fine textured soils in northeast, eastcentral, and central Indiana is about 221 lbs N / ac. The AONR for the remainder of the state (NC, SW, SC, and SE) is about 183 lbs N / ac. For more details on these recommendations see our current publication at: http://www.agry.purdue.edu/ext/corn/news/timeless/NitrogenMgmt.pdf
At the five Purdue locations where we conducted paired trials of corn following soy and corn following corn in 2007-2010, the average AONR for corn/corn was 44 lbs greater than for corn/soy. Based on $0.50 to $0.70/lb N and $7.00/bu corn, the average Economic Optimum N Rate (EONR) for corn following soybean was approximately 164, 203, and 172 lbs N / ac for WC+NW, NE+EC+C, and the remainder of the state, respectively. The EONR values for other combinations of N cost and grain price are listed in the Nitrogen Management Guidelines for Indiana or in the on-line N calculator for Indiana at this web site: http://extension.agron.iastate.edu/soilfertility/nrate.aspx.