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Nitrogen fertilization is essential for optimizing crop yields; however, it may potentially increase nitrous oxide (N2O) emissions. The study objective was to assess the ability of commercially available enhanced-efficiency N fertilizers to reduce N2O emissions following their application in comparison with conventional dry granular urea and liquid urea-ammonium nitrate (UAN) fertilizers in an irrigated no-till (NT) corn (Zea mays L.) production system. Four enhanced-efficiency fertilizers were evaluated: two polymer-coated urea products (ESN and Duration III) and two fertilizers containing nitrification and urease inhibitors (SuperU and UAN+AgrotainPlus). Nitrous oxide fluxes were measured during two growing seasons using static, vented chambers and a gas chromatograph analyzer. Enhanced-efficiency fertilizers significantly reduced growing-season N2O-N emissions in comparison with urea, including UAN. SuperU and UAN+AgrotainPlus had significantly lower N2O-N emissions than UAN. Compared with urea, SuperU reduced N2O-N emissions 48%, ESN 34%, Duration III 31%, UAN 27%, and UAN+AgrotainPlus 53% averaged over 2 yr. Compared with UAN, UAN+AgrotainPlus reduced N2O emissions 35% and SuperU 29% averaged over 2 yr. The N2O-N loss as a percentage of N applied was 0.3% for urea, with all other N sources having significantly lower losses. Grain production was not reduced by the use of alternative N sources. This work shows that enhanced-efficiency N fertilizers can potentially reduce N2O-N emissions without affecting yields from irrigated NT corn systems in the semiarid central Great Plains.

Nitrogen fertilization is essential for optimizing crop yields; however, it increases N2O emissions. The study objective was to compare N2O emissions resulting from application of commercially available enhanced‐efficiency N fertilizers with emissions from conventional dry granular urea in irrigated cropping systems. Nitrous oxide emissions were monitored from corn (Zea mays L.) based rotations receiving fertilizer rates of 246 kg N ha−1 when in corn, 56 kg N ha−1 when in dry bean (Phaseolus vulgaris L.), and 157 kg N ha−1 when in barley (Hordeum vulgare L. ssp. vulgare). Cropping systems included conventional‐till continuous corn (CT‐CC), no‐till continuous corn (NT‐CC), no‐till corn–dry bean (NT‐CDb), and no‐till corn–barley (NT‐CB). In the NT‐CC and CT‐CC systems, a controlled‐release, polymer‐coated urea (ESN) and dry granular urea were compared. In the NT‐CDb and NT‐CB rotations, a stabilized urea source (SuperU) was compared with urea. Nitrous oxide fluxes were measured during two growing seasons using static, vented chambers and a gas chromatograph analyzer. Cumulative growing season N2O emissions from urea and ESN application were not different under CT‐CC, but ESN reduced N2O emissions 49% compared with urea under NT‐CC. Compared with urea, SuperU reduced N2O emissions by 27% in dry bean and 54% in corn in the NT‐CDb rotation and by 19% in barley and 51% in corn in the NT‐CB rotation. This work shows that the use of no‐till and enhanced‐efficiency N fertilizers can potentially reduce N2O emissions from irrigated systems.

Remogna for their technical assistance. We also extend our appreciation to the anonymous reviewers who provided useful suggestions for improvement of this paper. This publication is the result of a FISR project funded by the Italian Ministry of Agriculture and Forestry. 1Mitigating the impact of fertilization on global warming: can leguminous green manure and compost help to reduce N 2 O and CO 2 emissions? ABSTRACT Alternative nitrogen fertilizers that stimulate low greenhouse gas emissions from soil are needed to reduce the impact of agriculture on global warming. Corn (Zea mais, L.) grown in a calcareous silt loam soil in northwestern Italy was fertilized with a municipal solid waste compost and vetch green manure (Vicia villosa, Roth.). Their potential to reduce N 2 O and CO 2 emissions was compared to that of urea (130 kg N ha -1 ). Gaseous fluxes were measured for two years in the spring (after soil incorporation of fertilizers) and in summer. In spring, the slow mineralization of compost reduced N 2 O emissions (0.11 % of supplied N) relative to urea (3.4 % of applied N), without an increase in CO 2 fluxes. Nitrous oxide (2.31 % of fixed N) and CO 2 emissions from rapid vetch decomposition did not differ from urea. When N 2 O and CO 2 fluxes were combined, compost reduced by 49% the CO 2 equivalent emitted following urea application. Vetch did not show such an effect. In summer, no fertilizer effect was found on N 2 O and CO 2 emissions. Compost proved to be potentially suitable to reduce CO 2 equivalent emitted after soil incorporation while vetch did not.For a thorough evaluation, net greenhouse gas emissions assessment should be extended to the entire N life cycle. Differences between calculated N 2 O emission factors and the default Tier 1 IPCC value (1%) confirmed the need for site-and fertilizer-specific estimations.Abbreviations: ΔCO 2 eq, increase of emitted CO 2 equivalent due to the applied fertilizer N respect to absence of fertilization; COM, fertilization with compost; CK, check plots not fertilized with N; EF, nitrous oxide emission factor of fertilizer N applied; GHG, greenhouse gas; LGM, fertilization with a leguminous green manure (hairy vetch); Ndfa, N derived from the atmosphere and fixed by a legume; PD, potential denitrification; PMN, N potentially mineralizable in anaerobiosis; SOC, soil organic carbon; SON, soil organic nitrogen; UR, fertilization with urea; WFPS, water-filled pore space.

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