Nitrous Oxide Emissions in Irrigated Corn as Affected by Nitrification Inhibitors
1992
Bronson, K. F. | Mosier, A. R. | Bishnoi, S. R.
Nitrous oxide and N₂ are the major denitrification products in irrigated corn (Zea mays L.). In addition, N₂O is considered a gas that contributes to global warming and stratospheric O₃ depletion. Minimizing N₂O emissions in cropping systems is therefore an economic as well as an important environmental concern. In a 1989 field experiment, the nitrification inhibitor encapsulated calcium carbide (ECC) (0, 20, or 40 kg CaC₂ ha⁻¹) or nitrapyrin (0.5 L a.i. ha⁻¹) was banded with urea (218 kg N ha⁻¹) 7 wk after planting corn. Between 1 and 14 wk after fertilization in 1989, N₂O losses of 3226, 1109, 1017, and 1005 g N₂O-N ha⁻¹ from urea alone, urea plus nitrapyrin, urea plus 20 kg ECC ha⁻¹, and urea plus 40 kg ECC ha⁻¹, respectively, were measured from vented chambers. Nitrous oxide fluxes were positively correlated with soil NO₃ levels, indicating that the nitrification inhibitors indirectly controlled N₂O emissions by preventing NO₃ from accumulating in the soil. Carbon dioxide emissions from the root zone were generally not affected by ECC or nitrapyrin. In 1990, losses of N₂O were less than in 1989 (1651 g N ha⁻¹ with urea alone), probably because there were fewer irrigations. Nitrapyrin and ECC addition to urea resulted in 980 and 459 g N ha⁻¹ N₂O being emitted the second year. Nitrification inhibitors appear to be a useful tool in mitigating N₂O emissions in agricultural systems.
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