Effect of fertilization rate on CH4 and N2O emission in paddy fields in Fuzhou plain
In order to determine the environmental effect of fertilizer rates, CH4 and N2 O emissions from paddy fields in Fuzhou Plain under three fertilizer regimes, namely, no fertilization (CK), normal rate of fertilization (TreatmentⅠ) and double rate of fertilization ( TreatmentⅡ) ,were measured using the static chamber-gas chromatograph technique. The results showed that:( 1) the accumulated CH4 emission fluxes was 7.67, 9.23, and 10.69 g·m-2 for CK, TreatmentⅠ, and TreatmentⅡwith average CH4 emis-sion fluxes of 3.47, 4.18, and 4.84 mg·m-2 ·h-1 , respectively. ( 2) Double rate of fertilization significantly enhanced CH4 emis-sion (P<0.05). (3)The accumulated N2O emission volume was -0.03, -0.05, and -0.06 mg·m-2 for CK, TreatmentⅠ, and TreatmentⅡwith the average N2O emission fluxes of-13.99,-22.77 , and-28.10μg·m-2·h-1, respectively. (4)N2O emission rate from the paddy fields under different treatments were not significantly different (P>0.05). (5)A highly significant correlation was found between CH4 emission and soil electric conductivity ( P<0.01) under all fertilizer regimes;but a negative correlation was found between N2 O emission and soil conductivity ( P<0.05) under normal rate of fertilization. Therefore, different correlation coef-ficients were found between CH4 and N2 O emission volumes under different fertilizer treatments and environmental factors such as soil pH, Eh, temperature, and water content. And lastly, (6)compounded greenhouse (warming) effect was 2 515.03, 2 989.07, and 3 450.45 kg·hm-2 , respectively, for CK, TreatmentⅠ, TreatmentⅡ, respectively. It was obvious that TreatmentⅡ( double rate of fertilization) had enhanced significantly the compounded greenhouse warming potentials in paddy fields.
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