Effects of winter covering crop residue incorporation on CH₄ and N₂O emission from double-cropped paddy fields in southern China

Abstract

Residue management in cropping systems is useful to improve soil quality. However, the studies on the effects of residue management on methane (CH4) and nitrous oxide (N2O) emission from paddy field in southern China are few. Therefore, the emissions of CH4 and N2O were investigated in double cropping rice (Oryza sativa L.) systems with different winter covering crops using the static chamber-gas chromatography technique to assess the effects of different covering crops on the emissions of greenhouse gases. The experiment was established in 2004 in Hunan Province, China. Three winter cropping systems were used: rice-rice-rape (Brassica napus L.) (T1), rice-rice-potato with straw mulching (Solanum tuberosum L.) (T2), and rice-rice with winter fallow (CK). A randomized block design was adopted in plots, with three replications. The results showed that T2 plots had the largest CH4 emissions during the early and late rice growing season with 12.506 and 32.991 g m(-2), respectively. When compared to CK, total N2O emissions in the early rice growth period and the emissions of the gas increased by 0.013 g m(-2) in T1 and 0.045 g m(-2) in T2, respectively. Similar results were obtained in the late rice growth period; the total N2O emissions increased by 0.027 g m(-2) in T1 and 0.084 g m(-2) in T2, respectively. The mean value of global warming potentials (GWPs) of CH4 and N2O emissions over 100 years was in the order of T2 > T1 > CK, which indicated CK and T1 was significantly lower than T2 (P < 0.05). This suggests that adoption of T1 would be beneficial for greenhouse gas emission mitigation and could be a good option cropping pattern in double rice cropped regions.

Fig. 1

Daily precipitation and mean temperature from May to October between 2012 and 2013 at the experimental site

Fig. 2

Device designed for air sampling

Fig. 3

CH₄ flux under different winter covering crops–double cropping rice systems during the early and late rice growing seasons in 2012 (a) and 2013 (b). T1 rice–rice–rape cropping system, T2 rice–rice–potato cropping system, CK rice–rice cropping system with winter fallow, ERT early rice transplanting, ERH early rice harvesting, and LRT late rice transplanting. CH₄ emission rate is the mean of values measured within each treatment (n = 3). Bars indicate standard deviation

Fig. 4

N₂O flux under different winter covering crops–double cropping rice systems during the early and late rice growing seasons in 2012 (a) and 2013 (b) T1 rice–rice–rape cropping system, T2 rice–rice–potato cropping system, CK rice–rice cropping system with winter fallow, ERT early rice transplanting, ERH early rice harvesting, and LRT late rice transplanting. CH₄ emission rate is the mean of values measured within each treatment (n = 3). Bars indicate standard deviation