Nitrous oxide and N2 are the major denitriflcation products in irrigated corn (lea mays L.). In addition, N2O is considered a gas that contributes to global warming and stratospheric O3 depletion. Minimizing NjO 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-') or nitrapyrin (0.5 L a.i. ha-1) was banded with urea (218 kg N ha-') 7 wk after planting com. Between 1 and 14 wk after fertilization in 1989, N2O losses of 3226, 1109,1017, and 1005 g N2O-N ha-' 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 NO, 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-' 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.
