Abstract
The objective of this study was to quantify soil methane (CH4) and nitrous oxide (N2O) emissions when converting from minimum and no-tillage systems to subsoiling (tilled soil to a depth of 40 cm to 45 cm) in the North China Plain. The relationships between CH4 and N2O flux and soil temperature, moisture, NH4 +-N, organic carbon (SOC) and pH were investigated over 18 months using a split-plot design. The soil absorption of CH4 appeared to increase after conversion from no-tillage (NT) to subsoiling (NTS), from harrow tillage (HT) to subsoiling (HTS) and from rotary tillage (RT) to subsoiling (RTS). N2O emissions also increased after conversion. Furthermore, after conversion to subsoiling, the combined global warming potential (GWP) of CH4 and N2O increased by approximately 0.05 kg CO2 ha−1 for HTS, 0.02 kg CO2 ha−1 for RTS and 0.23 kg CO2 ha−1 for NTS. Soil temperature, moisture, SOC, NH4 +-N and pH also changed after conversion to subsoiling. These changes were correlated with CH4 uptake and N2O emissions. However, there was no significant correlation between N2O emissions and soil temperature in this study. The grain yields of wheat improved after conversion to subsoiling. Under HTS, RTS and NTS, the average grain yield was elevated by approximately 42.5%, 27.8% and 60.3% respectively. Our findings indicate that RTS and HTS would be ideal rotation tillage systems to balance GWP decreases and grain yield improvements in the North China Plain region.
Highlights
CH4 and N2O play a key role in global climate change [1]
The soil absorption of CH4 increased from 13.53 mg?m22?h21 under harrow tillage (HT) to 16.72 mg?m22?h21 under HT conversion to subsoiling (HTS), from 15.59 mg?m22?h21 under rotary tillage (RT) to 18.20 mg?m22?h21 under RT conversion to subsoiling (RTS) and from 9.01 mg?m22?h21 under NT to 11.36 mg?m22?h21 under NT conversion to subsoiling (NTS), respectively
N2O emission increased after subsoiling (Fig. 2 D to F), which increased from 49.07 mg?m22?h21 under HT to 54.05 mg?m22?h21 under HTS and from 47.49 mg?m22?h21 under RT to 53.60 mg?m22?h21 under RTS
Summary
The emission of gas from disturbed soils is an especially important contributory factor to global change [2]. N2O is emitted from disturbed soil, whereas CH4 is normally oxidized by aerobic soils, making them sinks for atmospheric CH4 in dry farmland systems [3]. According to estimates of the IPCC [4], CH4 and N2O from agricultural sources account for 50% and 60% of total emissions, respectively. It is critical to reduce emissions of greenhouse gases (GHG) from agricultural sources. Many studies have reported that soil tillage has significant effects on CH4 and N2O emissions from farmland because the production, consumption and transport of CH4 and N2O in soil are strongly influenced by tillage methods [5,6,7,8]
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