Effects of Urea and Controlled Release Urea Fertilizers on Methane Emission from Paddy Fields: A Multi-Year Field Study

Abstract

A four-year (2008–2011) field study was implemented in a major rice-growing region of China to better understand the effect of urea and controlled release fertilier (CRF, thermoplastic resin-coated urea in this study) on CH4 emission from paddy fields. Over the four years, the average CH4 emission during the rice growing seasons was 76.9, 65.8 and 64.9 kg CH4 ha−1 in treatments CK (zero N), U (urea) and C (CRF), respectively. Urea and CRF significantly reduced CH4 emission by 14.4% and 15.6%, and increased average rice grain yield by 25.8% and 19.7% (P < 0.05), respectively, compared with treatment CK. Flooding duration would affect CRF's effect on CH4 emission from paddy fields. Under normal aeration conditions, CH4 emission tended to be 3.9%–15.2% lower in treatment C than in treatment U from 2009 to 2011, while it tended to be 4.2% higher under delayed aeration conditions in 2008. The findings suggest that mid-season aeration (MSA) starting on D30 (30 days after rice transplanting), just like the local practice, would optimize the CRF's effect on CH4 emission from rice fields in China. Over the four years, average rice yield did not differ between treatments U and C, and tended to be 5% lower in treatment C than in treatment U.