Abstract
Residue management in cropping systems is believed to improve soil quality. However, the effects of residue management on methane (CH4) and nitrous oxide (N2O) emissions from paddy field in Southern China have not been well researched. The emissions of CH4 and N2O were investigated in double cropping rice (Oryza sativa L.) systems with straw returning of different winter cover crops by using the static chamber-gas chromatography technique. A randomized block experiment with three replications was established in 2004 in Hunan Province, China, including rice–rice–ryegrass (Lolium multiflorum L.) (Ry-R-R), rice–rice–Chinese milk vetch (Astragalus sinicus L.) (Mv-R-R) and rice–rice with winter fallow (Fa-R-R). The results showed that straw returning of winter crops significantly increased the CH4 emission during both rice growing seasons when compared with Fa-R-R. Ry-R-R plots had the largest CH4 emissions during the early rice growing season with 14.235 and 15.906 g m−2 in 2012 and 2013, respectively, when Ry-R-R plots had the largest CH4 emission during the later rice growing season with 35.673 and 38.606 g m−2 in 2012 and 2013, respectively. The Ry-R-R and Mv-R-R also had larger N2O emissions than Fa-R-R in both rice seasons. When compared to Fa-R-R, total N2O emissions in the early rice growing season were increased by 0.05 g m−2 in Ry-R-R and 0.063 g m−2 in Mv-R-R in 2012, and by 0.058 g m−2 in Ry-R-R and 0.068 g m−2 in Mv-R-R in 2013, respectively. Similar result were obtained in the late rice growing season, and the total N2O emissions were increased by 0.104 g m−2 in Ry-R-R and 0.073 g m−2 in Mv-R-R in 2012, and by 0.108 g m−2 in Ry-R-R and 0.076 g m−2 in Mv-R-R in 2013, respectively. The global warming potentials (GWPs) from paddy fields were ranked as Ry-R-R>Mv-R-R>Fa-R-R. As a result, straw returning of winter cover crops has significant effects on increase of CH4 and N2O emission from paddy field in double cropping rice system.
Highlights
With the current rise in global temperatures, numerous studies have focused on greenhouse gases (GHG) emissions [1,2,3]
Sowing and seedling raising Paddy tillage Transplanting (16 cm616 cm) Urea were applied at 130.0 kg ha21 for top–dressed at tillering Drained out water and dried the soil at maximum tillering stage Wetting–drying alternation irrigation Grains were harvested Sowing and seedling raising Paddy tillage (The rate of early rice straw returning was 4 500.0 kg ha21) Transplanting (16 cm616 cm) Urea were applied at 156.5 kg ha21 for top–dressed at tillering Drained out water and dried the soil at maximal tillering stage Wetting–drying alternation irrigation Grains were harvested
We found that CH4 emission was low in paddy fields after transplanting during early rice–growing season, and increased with the decomposition of organic matters and growth of rice
Summary
With the current rise in global temperatures, numerous studies have focused on greenhouse gases (GHG) emissions [1,2,3]. Agriculture production is an important source of GHG emission [4]. In addition to carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) play important roles in global warming. In addition to industrial emissions, farmland is another important source of atmospheric GHG [7,8,9,10]. Numerous results indicate that rice (Oryza sativa L.) paddy field is a significant source of CH4 and N2O emissions [10,11]. The anaerobic conditions in wetland rice field are favorable for fostering CH4 emission [12]. The characteristics of CH4 and N2O emissions from paddy field and the reduction of emission have received attentions from scientists
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