Effect of the number of tillages in fallow season and fertilizer type on greenhouse gas emission from a rice (<i>Oryza sativa</i> L.) paddy field in Ehime, southwestern Japan
Creators: name: Toma, Yo
name: Oomori, Shingo
name: Maruyama, Asuka
name: Ueno, Hideto
name: Nagata, Osamu
Publisher: name: Taylor & Francis
Year: 2015
Subjects: subject: Microbiology
subject: FOS: Biological sciences
subject: FOS: Biological sciences
subject: Pharmacology
subject: 59999 Environmental Sciences not elsewhere classified
subject: FOS: Earth and related environmental sciences
subject: FOS: Earth and related environmental sciences
subject: 39999 Chemical Sciences not elsewhere classified
subject: FOS: Chemical sciences
subject: FOS: Chemical sciences
subject: Ecology
subject: 69999 Biological Sciences not elsewhere classified
subject: Developmental Biology
subject: Plant Biology

description: Agricultural fields, including rice (<i>Oryza sativa</i> L.) paddy fields, constitute one of the major sources of atmospheric methane (CH<sub>4</sub>) and nitrous oxide (N<sub>2</sub>O). Organic matter application, such as straw and organic fertilizer, enhances CH<sub>4</sub> emission from paddy fields. In addition, rice straw management after harvest regulates CH<sub>4</sub> emissions in the growing season. The interaction of tillage times and organic fertilizer application on CH<sub>4</sub> and N<sub>2</sub>O emissions is largely unknown. Therefore, we studied the effects of fallow-season tillage times and fertilizer types on CH<sub>4</sub> and N<sub>2</sub>O emissions in paddy fields in Ehime, southwestern Japan. From November 2011 to October 2013, four treatments, two (autumn and spring) or one (spring) in the first year, or two (autumn and spring) or three (autumn, winter, and spring) in the second year times of tillage with chemical or organic fertilizer application, were established. Gas fluxes were measured by the closed-chamber method. Increasing the number of tillage times from one to two decreased succeeding CH<sub>4</sub> emission and the emission factor for CH<sub>4</sub> (EF<sub>CH4</sub>) in the rice-growing season, suggesting that the substrate for CH<sub>4</sub> production was reduced by autumn and spring tillage in the fallow season. Higher EF<sub>CH4</sub> [1.8–2.0 kg carbon (C) ha<sup>−1</sup> d<sup>−1</sup>] was observed when more straw was applied (6.9–7.2 Mg ha<sup>−1</sup>) in the second year. Organic fertilizer application induced higher CH<sub>4</sub> emission just after the application as basal and supplemental fertilizers, especially at a lower straw application rate. This indicated that EF<sub>CH4</sub> in the organically managed fields should be determined individually. Organic fertilizer application with two tillage times induced N<sub>2</sub>O efflux during the rice-growing season in the second year, but N<sub>2</sub>O emissions were not affected by winter tillage. Although paddy fields can act as an N<sub>2</sub>O sink because of reduced soil conditions when straw application was high, application of organic C and nitrogen as fertilizer can enhance N<sub>2</sub>O production by the denitrification process during the growing season, especially in the ripening stage when soil anaerobic conditions became moderate. These results suggest that negative emission factors for N<sub>2</sub>O (EF<sub>N2O</sub>) can be applied, and EF<sub>N2O</sub> of organic fertilizer should be considered during the estimation of N<sub>2</sub>O emission in the paddy field.