Before you make that final decision on what to do about your fertility program this fall, let’s talk fertilizer one more time. Yes, the price is high. Yes, the price will go higher. Although you think you have made your final decision, that final decision needs to be based on all possible information from credible sources. So, let’s talk fertilizer one more time.

Some of this information may be repetitive. Some may be old news. But if there is one thing that is mentioned that may help you improve your fertility management program or improve your profitability, then a quick review had some value.

Visit with your dealer to find out why fertilizer prices are the way they are. You will hear about global demand, loss of retail marketing channels, and new financial structures for fertilizer suppliers.

A simple soil test can save money by identifying un-needed nutrients, as well as increase profits by identifying nutrients that need boosting. Here is a guide to soil testing.

If your soil test indicates the need for P & K, Extension fertility specialists John Sawyer and Antonio Mallarino at Iowa State say to apply P & K where the chance of yield increase is large and the yield increase will at least pay for the applied nutrient. If the soil tests show P & K are in the high to very high category, then enough may be “banked” that can be used next season. Withholding fertilizer may be an option you are considering, however the Extension Specialists say a soil test is the only way to know if that will work.

Apply the nutrient needs for both corn and soybeans prior to planting 2009 corn, unless rates for nutrients will drop prior to the planting of 2010 soybeans. A major reason is to keep the cost of application as low as can be.

Limestone will keep pH in balance and ensure your other nutrients will perform at optimum levels. Your soil pH should be at 6.5, and keep in mind that soybeans are more sensitive to soil acidity than corn, but in continuous corn, constant applications of N will increase soil acidity.

Sawyer and Mallarino also provide nitrogen recommendations and say there are not many opportunities to eliminate N when prices are high. They mention the use of manure and say there is not enough to go around for everyone. “If N fertilizer is in short supply or purchases have to be limited, it is better to apply some N to all fields than to skip fields (other than corn after alfalfa) as the largest yield gains come from the first increments of applied N.”

The corn nitrogen rate calculator will help you compare specific prices of corn and the specific price of anhydrous ammonia. The rates are the same regardless of when it is applied, and will provide a maximum return to nitrogen. The Iowa State fertility researchers say “Typically best efficiency is obtained with spring or split spring/sidedress application. Having plant-available N in the root zone is important for good early corn growth, and especially for corn following corn.

To retain nitrogen in the soil where it will be available to the 2009 crop, Extension fertility specialist Fabian Fernandez at the University of Illinois recommends the use of a nitrification inhibitor if the soil temperature exceeds 50 degrees Fahrenheit. “To avoid volatilization losses during application, make sure the soil is neither too wet nor too dry to secure adequate closure of the soil behind the applicator knife. Also, it is important to apply at the proper depth; for fine-textured soils, 6 to 8 inches is sufficient to keep NH3 gas from escaping the soil.”

If you have many stalks in the field from continuous corn operations, Fernandez says there is no great benefit for fall application of nitrogen to increase microbial activity against cellulose-laden residue.

With high prices, Fernandez says it is critical to have every pound of fertilizer going to corn yield, and he agrees with his Iowa State colleagues that spring side dress applications are more effective than fall because of the potential loss over the winter.

Summary:
High prices for fertilizer have challenged crop profitability, but it is almost impossible to grow high yielding corn without a good fertility program. To increase the efficiency of your fertilizer dollar, a soil test will indicate whether nutrients are needed or can be banked for a future year. Lime will keep pH in balance, and may be needed behind continuous corn, because of the high acidity rates left by nitrogen. When applying fall nitrogen, observe all of the recommendations about soil temperatures and the use of a nitrification inhibitor.