Abstract

Application of 56, 112, or 224 kg N ha⁻¹ as ammonium nitrate (NH₄NO₃) (AN) to barley (Hordeum vulgare) plots in northeastern Colorado led to a marked, but short-lived, increase in nitrous oxide (N₂O) emissions that was linearly related to the amount of AN applied. The AN treatment effects became statistically insignificant after about 6 weeks. Compared with total N₂O emissions of 0.54 kg N ha⁻¹ from the control plots, totals from the AN-treated plots ranged from 0.93 to 1.43 kg N ha⁻¹, representing an average 0.5% of the fertilizer added. Nitrous oxide emissions from plots treated with 16.7 metric tons ha⁻¹ dry anaerobically digested sewage sludge (SS) totaled 1.09 kg N ha⁻¹ and exhibited temporal variability similar to that of AN-treated plots, while the emissions from plots treated with 83.5 metric tons SS ha⁻¹ were significantly larger than from the other treatments throughout the 155-day study period and totaled 4.19 kg N ha⁻¹. The increase in N₂O emissions that results from application of organic or inorganic N amendments appears to be much smaller than assumed by models developed to describe the effect of agricultural fertilizers upon stratospheric ozone depletion.

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