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Source: Jim Morrison, Extension Educator, Crop Systems, Rockford Extension Center, University of Illinois, Phone 815-397-7714; FAX 815-397-8620, E-mail morrison@uiuc.edu Producers and agribusiness dealers may be aware that university agronomists from a number of Corn Belt states have been collaborating recently on a new approach to making nitrogen rate recommendations for corn. This approach uses recent research data, and applies economics to the decision on nitrogen rates. Over the last few months, nitrogen prices have risen sharply, raising questions about what nitrogen rates should be for the 2006 corn crop. Following is a summary, prepared by Emerson Nafziger and Robert Hoeft, University of Illinois Department of Crop Sciences, of what these nitrogen rate recommendations will look like for Illinois:
- The Proven Yield method now used for nitrogen (N) recommendations produces N rates that are higher than rates needed to maximize return to N, especially for corn that follows soybean, where yield levels are high, and when the N price increases.
- The guidelines will now be to apply N rates within a range, defined as the N rates that provide returns close to the maximum economic return to N. These ranges will be based on N response data from some 250 Illinois trials.
- The recommended range will change when the price ratio between N and corn changes.
- There will be separate ranges for corn following soybean (SC) and corn following corn (CC). The "soybean N credit" will no longer be subtracted, though it will be included directly, since the SC range will be based on SC research, and the CC range will be based on CC research. [Adding the "soybean N credit" to the SC recommended range to produce "total N supply" might help with acceptability of this approach, but should no longer be subtracted from the recommended CC range or otherwise be part of the recommendation.]
- Calculating separate ranges based on the data suggests that N rate ranges for Southern and Central Illinois are very similar, but that rates for Northern Illinois are actually less than those for the rest of the state. Having a single recommended range for all of Illinois, while conservative for Northern Illinois, may be an acceptable approach until more data become available.
- For corn following corn, there is some correlation between yield and the N rate it takes to produce that yield, indicating that some adjustment based on yield is justified. We suggest using the expected yield to move to higher or lower rates, while staying within the suggested range of rates.
- Using a corn price of $2.00 per bushel and an N price of $0.30 per lb. ($492 per ton of anhydrous ammonia), the recommended range of N rates for corn following soybean in Illinois is 122 to 162 lb N per acre. This range drops by about 10 lb. if the N price increases by 6 cents per lb. of N ($100 per ton of anhydrous ammonia), providing the corn price stays the same.
- For corn following corn using the same prices, the recommended range is 137 to 174 lb N per acre. Within this range, increase the N rate by 0.4 lb of N for each bushel of yield expected above 148 bushels per acre. [If yield is expected to be 180 bu. per acre, add 32 x 0.4 = 13 lb N to the 156 lb N that is the midpoint, so use at least 169 lb N.]
- Producers and advisers will need to decide where to set N rates within a recommended range. This decision can involve risk management philosophy, previous experience with N rates, and possible considerations regarding N movement into the environment.
This topic will be discussed in further detail at various Extension meetings this winter. The above information was taken from the University of Illinois Pest Management and Crop Development Bulletin, issue 23, October 7, 2005.
by Editor, theCity1.com
November 13, 2005
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