Perhaps you should file this one under 'it's too good to last, or the other shoe will drop,' but $7 per bushel corn is of the charts. It's so off the charts that when Bob Nielsen, Purdue University agronomist, updated his publication and table for figuring out how much N to recommend, he shut the chart off at $6 as the top price.
The amount to put on varies with the cost of N and the price of corn. The higher the cost of N, the less N you can put on before reaching the economic optimum level. Basically that's the point at which the next unit of N applied doesn't produce enough extra corn to pay for that last unit of N applied.
Likewise, the higher the price of corn, the more N you can afford to put on, even at higher prices for N. We observed that the chart ended at $6 but farmers were talking about $7 corn. Nielsen obliged by expanded the chart. You can find the chart and article on his www.KIng.com Corn website, or at the Chat'n Chew Cafe. These are two of the most outstanding Web sites for corn information on up-to-date topics in the country.
Nielsen wasn't taking any chances. I suggested he run it to $10, but he thought that a bit bold. However, he did run the chart through $9 per bushel corn, just in case. Many people are hoping that doesn't come around, because it could trigger reactions that may be detrimental in the long run. Don't look for that sharp of an increase unless drought enters the weather picture and it becomes a weather market early in the season.
The 2011 late winter was setting up much like 1988, which brought spring and early summer drought, until 10 days ago. Now soils across good portions of the Midwest are saturate. Ag climatologist Greg Soulje, Chicago, is now calling for an active spring weather pattern with above normal rainfall in many areas.
If you check Nielsen's chart, you'll find there's not a lot of difference in pound of N per acre recommended at $7 corn vs $6 corn. Unless you've got a very accurate applicator, it may not be possible to fine-tune down to such differences. But following the chart should put you in the ballpark.
Note that Nielsen's numbers are strictly for Indiana, and he even breaks Indiana into three sections, based on response differences he and Jim Camberato have seen on different types of soils. If you farm in other states, you might check the Nitrogen rate calculator published on the Web by Iowa State University. All are based on years of documented, properly run test plots on both university and cooperator farms.