Nutrient Management Research Database

Fertilizer application in crop production agriculture has been identified as a major source of the greenhouse gas nitrous oxide. Thus, management strategies that increase fertilizer N use efficiency will reduce N₂O emission. Anhydrous ammonia applied to cropland in the fall is recognized as a management practice that increases the risk of N loss from the rooting zone, however, this practice is still common in the U.S. Midwest Corn Belt. The nitrification inhibitor, nitrapyrin has been shown to decrease soil N losses during the fall and spring, and maintain fertilizer N availability to the crop. Additionally, nitrification inhibitors have shown promise in reducing soil N₂O emissions. However, there have been no studies evaluating the effectiveness of nitrapyrin to reduce annual N₂O emissions from land receiving fall-applied anhydrous ammonia. This study was conducted over 2 years to measure N₂O emissions from corn plots with fall-applied anhydrous ammonia with and without nitrapyrin. Based on soil NO₃ and NH₄ analyses, we observed that nitrapyrin delayed nitrification, and in 1 year, reduced late fall/early spring N₂O emission. However, annual N₂O emissions were not significantly reduced. Significantly higher corn grain yields were observed in the nitrapyrin treatment in both years.

This study investigated the effectiveness of the nitrification inhibitor nitrapyrin in reducing nitrous oxide (N₂O) emissions from fall-applied anhydrous ammonia in a corn cropping system.

The fertilizer was applied at either 80 lbs N/ac or 150 lbs N/ac.

Nitrapyrin was applied at the rate of 0.1 gal/ac.

N2O emissions were measured for a complete year at one site and two complete years at a second site.

Soil was sampled for nitrate and ammonium at each gas sampling date.

Nitrapyrin was effective at limiting the rate of nitrification.

While late fall/early spring N₂O emissions were reduced by nitrapyrin usage, overall seasonal emissions did not differ.

Using nitrapyrin increased corn yields by 6.5% on average, from 183 bu/ac to 195 bu/ac.

The climate in Iowa is quite different from California's, so one shouldn't expect to replicate these results in California.