Soil-surface carbon dioxide emission following nitrogen fertilization in corn

Improvement in use efficiency of N fertilizers can potentially better sustain agriculture by reducing N2O emissions from soils, but little is known about its impact on soil CO2 emissions. A study, involving both a field experiment and a laboratory incubation, was conducted in eastern Canada to determine the N fertilization effect on soil CO2 emissions. In laboratory, we incubated nine different types of soil with and without 150 kg N ha−1 as KNO3 or (NH4)2SO4. The N-fertilized soils had lower CO2 emissions compared with the no-N control soils for six of them. Among fertilizer sources, emissions of CO2 were on average 22% lower with KNO3 than with (NH4)2SO4. The field experiment conducted on a clay soil included three sources of N (urea-NH4NO3, CaNH4NO3, and aqua NH3) at 0–200 kg N ha−1 band-incorporated at the six-leaf corn stage. Under field conditions, most CO2 was emitted between N application and grain maturity with cumulative seasonal soil emissions greater in the control (4.9 Mg C ha−1) than in the ...