Abstract
Quantifying carbon (C) sequestration in paddy soils is necessary to help better understand the effect of agricultural practices on the C cycle. The objective of the present study was to assess the effects of tillage practices [conventional tillage (CT) and no-tillage (NT)] and the application of nitrogen (N) fertilizer (0 and 210 kg N ha−1) on fluxes of CH4 and CO2, and soil organic C (SOC) sequestration during the 2009 and 2010 rice growing seasons in central China. Application of N fertilizer significantly increased CH4 emissions by 13%–66% and SOC by 21%–94% irrespective of soil sampling depths, but had no effect on CO2 emissions in either year. Tillage significantly affected CH4 and CO2 emissions, where NT significantly decreased CH4 emissions by 10%–36% but increased CO2 emissions by 22%–40% in both years. The effects of tillage on the SOC varied with the depth of soil sampling. NT significantly increased the SOC by 7%–48% in the 0–5 cm layer compared with CT. However, there was no significant difference in the SOC between NT and CT across the entire 0–20 cm layer. Hence, our results suggest that the potential of SOC sequestration in NT paddy fields may be overestimated in central China if only surface soil samples are considered.
Highlights
Global surface temperatures have increased by 0.88uC since the late nineteenth century [1]
The observed climate changes are caused by the emission of greenhouse gases (GHGs) mainly through anthropogenic activities
Wassmann et al [34] and Lu et al [35] indicated no significant effect of N fertilizer application on CH4 emissions from paddy fields in Zhejiang Province, China
Summary
Global surface temperatures have increased by 0.88uC since the late nineteenth century [1]. The observed climate changes are caused by the emission of greenhouse gases (GHGs) mainly through anthropogenic activities. Rice paddies are an important source of atmospheric CH4. The amount of CH4 emitted from wetland paddy fields accounts for 10% to 20% of the total CH4 emissions (i.e. 50 Tg yr to 100 Tg yr21) [2]. The rice production of China exceeds that of any other country, accounting for 30% of the world total [3]. Agricultural activity affects CH4 and CO2 emissions, contributing 39% of the excess CH4 and 1% of the excess CO2 to global emissions [4]. CH4 emissions from paddy fields under different agricultural management practices in China are relevant to the discussion of the global C cycle and climate changes
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