Harvest is rapidly coming to a close. Even before the combines leave the fields farmers are being asked to make decisions about next year's crop. These include fertilizer and seed decisions that can easily cost the farmer over $100,000.

Seed dealers are asking farmers to select their corn hybrids for next year. Companies will offer their recommendations and plot data to promote their own products. Many farmers also utilize the University of Illinois, Crop Science Department's variety testing program to supply them with an unbiased information source. The quickest way to get the trial results is on-line at http://vt.cropsci.uiuc.edu. The 2008 soybean results are posted and corn will be posted by Monday, February 10.

The next decision for many farmers will concern when and if they should apply fall nitrogen fertilizer for next years corn crop. Let me start by reminding everyone that fall is the least efficient time to apply nitrogen fertilizer and when anhydrous ammonia costs $1100 a ton that is a big concern. I realize that from a labor, workload management and price forecasting standpoint that many farmers feel it necessary to fall apply. So if you feel you must please follow these guidelines to help protect your investment and the environment.

The Illinois Agronomy Handbook states that fall nitrogen applications should not start until soil temperatures at the 4-inch level have dropped to 50 degrees. This last weeks warm weather had us over the 50 degree level in the Champaign area. Farmers can check on soil temperatures from around the state at the State Water Survey website, www.isws.illinois.edu/warm/soiltemp.asp.

Remember that even with cool soil temperatures the conversion doesn't actually stop until the soil reaches 32 degrees. How much N you loose is dependent on time and temperature. We can't predict what the temperatures will be for the rest of the fall and winter. The longer you delay application the better your chances for maximum availability.

The current high price of nitrogen makes it very costly to over apply. Economically, you get the highest rate of return on those first dollars invested in nitrogen fertilizer and as the response starts to decrease there comes a point that an additional dollar of nitrogen returns less than a dollar's worth of yield. That point is the maximum return to nitrogen, MRTN. This curve changes as the price of nitrogen and the price of corn changes.

You can calculate your own MRTN by going on the web to an on-line calculator that allows you to enter your prices. The calculator will create a graph with three lines. One line will be a curve rising to a plateau that plots the Gross Return to N. A second line shows the angled rising straight line of Nitrogen Fertilizer Cost. The third is a dome shaped curve plotting the Net Return to N. The highest point on the Net Return to N curve is the MRTN.

The top of this Net Return to N curve is relatively flat. This indicates that applying a little more or less nitrogen than the MRTN, economically, doesn't make a big difference. That is why with the new recommendation system we talk about a range of optimum rates.

The easiest way to get to the website is do a Google search for "n-rate calculator." Iowa State is the host for this multi-state effort; make sure you pick Illinois, in the first selection box, so the calculator will use the Illinois data.