Effect of Slow/Controlled Release Fertilizers on CH₄ and N₂O Emissions From Helianthus tuberosus Field on Tidal Flat During Growing Season

A field experiment, designed to have seven treatments,i.e. U+DCD(urea plus dicyandiamide),U+HQ(urea plus hydroquinone),UF(urea formaldehyde), CMCU(Ca-Mg-P-coated urea),PCU(polymer-coated urea),SCU(sulfur-coated urea)and CK or U(urea), was conducted to explore effects of some typical slow-release fertilizers on methane (CH₄) and nitrous oxide (N₂O) emissions from Helianthus tuberosus fields on tidal flat in Dafeng of Jiangsu Province during its growing season in 2010.Fluxes of CH₄ and N₂O emissions from the field were measured simultaneously with the static chamber-GC method.Results show that in terms of seasonal CH4 emission, the 7 treatments followed the order of U > PCU > UF > SCU > CMCU > U+HQ > U+DCD, emitting 1.25, 0.59, 0.43, 0.27, 0.25, 0.26 and -0.21 kg•hm^-2, respectively. Compared with urea, the slow/controlled-release nitrogen fertilizers reduced seasonal CH₄ emissions by about 53%-80%, but did not vary much among themselves. In terms of seasonal N₂O emission, the treatments followed the order of PCU > SCU > CMCU > U > UF > U+HQ > U+DCD, emitting 2.94, 2.44, 2.27, 2.24, 1.77, 1.47 and 1.34 kg•hm^-2, respectively. Relative to urea, chemically-altered fertilizers reduced seasonal N₂O emission by 21%–40%, whereas physically-altered fertilizers increased total N₂O emission by 1%–31%. The findings suggest that from the aspect of the global warming potential, all the chemically altered nitrogen fertilizers display significant emission reducing effect.