Modeling impacts of farming management alternatives on CO2, CH4, and N2O emissions: A case study for water management of rice agriculture of China

Authors

Changsheng Li, University of New Hampshire - Main CampusFollow
Steve Frolking, University of New Hampshire - Main CampusFollow
Xiangming Xiao, University of New Hampshire - Main Campus
B Moore, University of New Hampshire - Main CampusFollow
Stephen Boles, University of New Hampshire - Main Campus
Jianjun Qiu, Chinese Academy of Agricultural Science
Yao Huang, Nanjing Agricultural University
William A. Salas, University of New Hampshire - Main Campus
Ronald Sass, Rice University

Abstract

Since the early 1980s, water management of rice paddies in China has changed substantially, with midseason drainage gradually replacing continuous flooding. This has provided an opportunity to estimate how a management alternative impacts greenhouse gas emissions at a large regional scale. We integrated a process-based model, DNDC, with a GIS database of paddy area, soil properties, and management factors. We simulated soil carbon sequestration (or net CO₂ emission) and CH₄ and N₂O emissions from China's rice paddies (30 million ha), based on 1990 climate and management conditions, with two water management scenarios: continuous flooding and midseason drainage. The results indicated that this change in water management has reduced aggregate CH₄ emissions about 40%, or 5 Tg CH₄ yr⁻¹, roughly 5–10% of total global methane emissions from rice paddies. The mitigating effect of midseason drainage on CH₄ flux was highly uneven across the country; the highest flux reductions (>200 kg CH₄-C ha⁻¹ yr⁻¹) were in Hainan, Sichuan, Hubei, and Guangdong provinces, with warmer weather and multiple-cropping rice systems. The smallest flux reductions (<25 kg CH₄-C ha⁻¹ yr⁻¹) occurred in Tianjin, Hebei, Ningxia, Liaoning, and Gansu Provinces, with relatively cool weather and single cropping systems. Shifting water management from continuous flooding to midseason drainage increased N₂O emissions from Chinese rice paddies by 0.15 Tg N yr⁻¹ (∼50% increase). This offset a large fraction of the greenhouse gas radiative forcing benefit gained by the decrease in CH₄ emissions. Midseason drainage-induced N₂O fluxes were high (>8.0 kg N/ha) in Jilin, Liaoning, Heilongjiang, and Xinjiang provinces, where the paddy soils contained relatively high organic matter. Shifting water management from continuous flooding to midseason drainage reduced total net CO₂emissions by 0.65 Tg CO₂-C yr⁻¹, which made a relatively small contribution to the net climate impact due to the low radiative potential of CO₂. The change in water management had very different effects on net greenhouse gas mitigation when implemented across climatic zones, soil types, or cropping systems. Maximum CH₄ reductions and minimum N₂O increases were obtained when the mid-season draining was applied to rice paddies with warm weather, high soil clay content, and low soil organic matter content, for example, Sichuan, Hubei, Hunan, Guangdong, Guangxi, Anhui, and Jiangsu provinces, which have 60% of China's rice paddies and produce 65% of China's rice harvest.

Department

Earth Sciences, Earth Systems Research Center

Publication Date

9-2005

Journal Title

Global Biogeochemical Cycles

Publisher

Wiley

Digital Object Identifier (DOI)

10.1029/2004GB002341

Document Type

Article

Recommended Citation

Li, C., S. Frolking, X. Xiao, B. Moore III, S. Boles, J. Qiu, Y. Huang, W. Salas, and R. Sass (2005), Modeling impacts of farming management alternatives on CO2, CH4, and N2O emissions: A case study for water management of rice agriculture of China, Global Biogeochem. Cycles, 19, GB3010, doi:10.1029/2004GB002341.

Rights

Copyright 2005 by the American Geophysical Union.