An N inhibitor may be considered if there is some worry about N loss from early application either through tile drainage or denitrification. Research in Minnesota has shown a benefit from inhibitors when used with spring-applied N. Two chemicals that have been shown to slow nitrification are Nitrapyrin, the active ingredient in N-serve, and Instinct, or DCD. These are the only two inhibitors shown to consistently slow the conversion of ammonium to nitrate. The length of these chemicals' effectiveness is governed by soil moisture and temperature. This is because Nitrapyrin and DCD reduce the microbial populations of the bacteria that convert ammonium to nitrate.

If the temperatures are warm and the soil is dry, there is concern of urea volatilize before it can convert to ammonium. Agrotain is a product used to slow the activity of urease, which converts urea to ammonia, and the best use for this product is when urea is surface applied and not incorporated. Normally it takes an average of 0.25 in. of rainfall to effectively incorporate urea into the soil. Agrotain extends the amount of time for this to occur.

In summary, keep your tillage operations few in number and shallow to reduce soil moisture loss. If you made fall N applications and are concerned about how much N is left, you should seriously consider using the supplemental N decision tool to time a sidedress N application. If you did not apply N in the fall on heavier textured soils, you may want to consider using a soil test for nitrate this spring. If you have sandy soils, follow established best management practices for nitrogen application. These practices include side-dress application of N. Finally, the use of a nitrification inhibitor or urease inhibitor will depend on the local soil situations and the weather this spring.