Friday, September 13, 2013

New paper finds rice crops are a net source of CO2 to the atmosphere

A new paper published in Atmospheric Environment finds rice crops in China are a net source of CO2 and methane [CH4] to the atmosphere. 

CO2 flux in 2011 shown in top graph, 2012 in bottom graph. Early and late rice are the 2 crops planted each year in "double rice cropping systems." Positive values indicate a net source of CO2 to the atmosphere. 

Emissions of CH4 and CO2 from double rice cropping systems under varying tillage and seeding methods

  • a MOA Key Laboratory of Crop Ecophysiology and Farming System in the Middle Reaches of the Yangtze River, PR China
  • b College of Plant Science and Technology, Huazhong Agricultural University, Wuhan 430070, PR China


No-tillage significantly decreased CH4 and CO2 emissions from double rice cropping systems.
Compared with transplanting seedlings, throwing of seedlings significantly reduced CH4 and CO2emissions.
The no-tillage in combination with throwing of seedlings can more effectively decrease carbon emissions.


A two-year field experiment was conducted to investigate the effects of different tillage (no-tillage [NT] and conventional tillage [CT]) and seeding methods (transplanting seedlings [TPS] and throwing of seedlings [ST]) on methane (CH4) and carbon dioxide (CO2) emissions from double rice cropping systems in central China. The CH4 and CO2 fluxes for early rice ranged from −2.52 mg m−2 h−1 to 125.0 mg m−2 h−1 and from 99.3 mg m−2 h−1 to 1463.6 mg m−2 h−1, respectively, whereas the fluxes for late rice varied from −7.22 mg m−2 h−1 to 242.3 mg m−2 h−1 and from 180.6 mg m−2 h−1 to 2219.0 mg m−2 h−1, respectively. Compared with NT, CT significantly increased (P < 0.05) the CH4 and CO2 emissions, where the seasonal total CH4emissions from the CT treatment were 1.75–2.10 times of those from the NT treatment for early rice and 1.64–1.79 times for late rice. Moreover, compared with the CT treatment, the NT treatment significantly reduced seasonal total CO2 emissions by 19%–33% for early rice (P < 0.05) and by 27%–31% for late rice (P < 0.05). The seeding methods significantly affected CH4 and CO2 emissions. Compared with TPS, ST significantly decreased seasonal total CH4 and CO2 emissions by 15%–40% (P < 0.05) and 19%–33% (P < 0.05) for early rice, and by 38%–47% (P < 0.05) and 19%–22% (P < 0.05) for late rice, respectively. These results may be attributed to reduced root growth and aboveground biomass. Therefore, simplified cultivation technologies are effective for reducing carbon emissions from double rice cropping systems in central China, and the combination of NT with ST can more effectively decrease carbon emissions.


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