Eliminating NH3,NO and N2O emissions simultaneously in a wheat field by urea point placement
Traditional surface application of urea often leads to the large amount of reactive nitrogen(N)losses,such as NH3 and NOx emissions,which have substantial impacts on the air pollution of Chinese cities,especially in winter.Urea point placement may have profound influences on NH3 and NOx emissions due to the concentrated N-fertilizer under root zone,but there has no such information available in winter wheat fields.A field experiment in a winter wheat field conducted which included three treatments:traditional 3-split urea broadcasting(CT);one-time urea point placement(PP),and CK without N.The results demonstrated that the total loss of NH3 from the point placement was negligible due to minimal NH4+-N diffusion into the surface soil layer,which was only 0.7%of the total applied N and 80%lower than that of the broadcasting treatment.The point placement treatment notably minimized the daily NO fluxes,and its total NO emission only accounted for 0.1%of the applied N.Compared with the broadcasting treatment,the point placement treatment reduced the wheat seasonal N2O emission by 25%,which accounted for 0.6%of the total nitrogen application.Negligible NO and N2O emission in the point placement treatment was attributable to the narrow range of NH4+movement(4-13 cm below the soil surface),high concentration around fertilizer placement and low winter temperature suppressed the microbial nitrification.The point placement treatment produced similar wheat yield compared to broadcasting due to the long-lasting fertilization effects.In conclusion,urea point placement could provide environmental benefits without sacrificing wheat yield in winter wheat cropping systems.
urea point placementNH3 volatilizationNO emissionN2O emissionintensive wheat cropping system
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