Reducing Gas Emissions from Ratooning Rice Field Using Controlled Nitrogen Fertilization and Alternate Wetting-drying Irrigation

Abstract

【Background and objective】 Rice field is an important source of greenhouse gases and how to reduce its gas emissions plays an important role in battling global warming. The aim of this paper is to investigate the feasibility and efficacy of using controlled nitrogen fertilization and irrigation management to reduce gas emissions from ratooning rice field. 【Method】 The experiment was conducted in a field using static chambers. In situ gas emissions were measured using gas chromatography. The experiment compared two irrigation methods: conventional irrigation and alternate wetting and drying irrigation, and five controlled nitrogen fertilizations: fertilization used by local farmers (FFP), applying the fertilizers in the root zone at the depth of 5 cm (RF1) and 10 cm (RF2) below the soil surface either separately, or in combination (RF3); no fertilization was taken as the control (CK). 【Result】 Compared to FFP, controlled fertilization RF1, RF2 and RF3 reduced emissions of CH4, N2O and CO2 by 49%~76%, 55%~81% and 57%~69% respectively (P<0.05) under conventional irrigation, and by 52%~77%, 52%~73% and 61%~75% respectively (P<0.05) under alternate wetting-drying irrigation. We also found that after changing to alternate wetting-drying irrigation, fertilization FFP, RF1, RF2 and RF3 reduced global warming potential by 3%, 10%, 13% and 11% (P<0.05), respectively, compared with their associated potentials at conventional irrigation. Compared with FFP, controlled fertilization RF3 under conventional and alternate wetting-drying irrigation increased the yield of ratoon rice by 7% and 11%, both at significant level, respectively. 【Conclusion】 Controlled nitrogen fertilization to the root zone not only reduces greenhouse gas emissions but also increases rice yield. Apart from saving water, changing from conventional irrigation to alternate wetting and drying irrigation increases yield and reduces greenhouse gas emissions, both at significant levels. Their combination can be used as an improved agronomic practice for ratooning rice production in south China.

Keywords

• ratoon rice
• irrigation method
• root-zone fertilization
• gas emissions
• greenhouse warming potential