Effect of Anhydrous Ammonia Fertilization on Emission of Nitrous Oxide from Soils

A simple method was developed for accurate injection of anhydrous ammonia in field studies to assess the effects of this fertilizer on emissions of nitrous oxide (N 2 O) from soils. Use of this method and of a chamber technique for measurement of N 2 O emissions showed that fertilization of three Iowa soils with anhydrous ammonia (250 kg N/ha) led to a very marked increase in emission of N 2 O. Emissions of N 2 O‐N from the fertilized soils in 139 days ranged from 12.1 to 19.6 kg/ha and averaged 15.6 kg/ha. The corresponding emissions from the unfertilized soils ranged from 1.7 to 2.5 kg/ha and averaged 2.0 kg/ha. Most of the N 2 O evolved from the fertilized soils was produced within 42 days after fertilization, and N 2 O emissions from these soils 96 days after fertilization were not appreciably greater than those from the corresponding unfertilized soils. The fertilizer‐induced emissions of N 2 O‐N observed after application of anhydrous ammonia greatly exceeded those detected in similar field studies using other N fertilizers and represented 4.0–6.8% of the fertilizer N applied.