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

• Chengfang Li^a, b, , , , 
• Zhisheng Zhang^a, b, 
• Lijin Guo^a, b, 
• Mingli Cai^a, b, 
• Cougui Cao^a, b, , 

• ^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

Highlights

•

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.

Abstract

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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