Effects of mild alternate wetting and drying irrigation and rice straw application on N2O emissions in rice cultivation
- 1Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang 110016, China
- 2Engineering Laboratory for Green Fertilizers, Chinese Academy of Sciences, Shenyang 110016, China
- 3University of Chinese Academy of Sciences, Beijing 100049, China
- 4Institute of Tillage and Cultivation, Liaoning Academy of Agricultural Sciences, Shenyang 110161, China
- 5Liaoning Key Laboratory of Conservation Tillage in Dry Land, Shenyang 110161, China
- 6National Engineering Laboratory for Soil Nutrient Management, Shenyang 110016, China
- 1Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang 110016, China
- 2Engineering Laboratory for Green Fertilizers, Chinese Academy of Sciences, Shenyang 110016, China
- 3University of Chinese Academy of Sciences, Beijing 100049, China
- 4Institute of Tillage and Cultivation, Liaoning Academy of Agricultural Sciences, Shenyang 110161, China
- 5Liaoning Key Laboratory of Conservation Tillage in Dry Land, Shenyang 110161, China
- 6National Engineering Laboratory for Soil Nutrient Management, Shenyang 110016, China
Abstract. The shortage of water resources and the decline in soil organic matter (SOM) are important limiting factors affecting the improvement of rice productivity, while alternate wetting and drying (AWD) irrigation and rice straw return are considered favorable mitigation measures. However, its impact on rice yield and greenhouse gas (GHG) emissions, especially nitrous oxide (N2O) emissions, needs to be further clarified, which is essential for the development of agronomic measures for water savings, soil fertilization and GHG reduction. Therefore, we explored the effects of mild AWD irrigation combined with rice straw return on N2O emissions and rice yield through rice pot experiments. This study showed that N2O emissions were mainly affected by urea application and irrigation methods, and urea application was the main reason. Compared with continuous flooding (CF) irrigation, mild AWD irrigation increased cumulative N2O emissions, with an average increase of 28.8 %. In addition, adding rice straw to mild AWD irrigation further stimulated N2O emissions. Compared with CF irrigation, mild AWD irrigation increased the yield-scaled N2O emissions, and the addition of rice straw further promoted the yield-scaled N2O emissions under mild AWD irrigation but reduced the global warming potential (GWP) by 62.9 %. Under the condition of urea application, compared with CF irrigation, mild AWD irrigation reduced nitrogen uptake by rice in the soil and rice aboveground biomass without reducing rice yield. Therefore, mild AWD irrigation combined with rice straw return is a promising agronomic measure to ensure rice yield, reduce the greenhouse effect and maintain or improve soil fertility.
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Kaikuo Wu et al.
Status: open (until 06 Aug 2022)
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RC1: 'Comment on egusphere-2022-429', Anonymous Referee #1, 29 Jun 2022
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The authors conducted a laboratory pot experiment to investigate the effects of mild alternate wetting and drying (AWD) irrigation and rice straw application on N2O emissions in rice cultivation through 15N tracer technique. Their results showed that mild AWD irrigation increased cumulative N2O emissions by 28.8%. Adding rice straw to mild AWD irrigation further stimulated N2O emissions. These evidences have significance for monitoring N2O emissions in paddy fields. However, I still have some comments here for the authors to address before it’s ready for publication.
For several places, there are something important missing for the authors to have their conclusions.
For example, in abstract L33-36 “mild AWD reduced GWP by 62.9%”, but there is neither GWP calculation nor CH4 data reported, which also lacks CO2 data.
L39-L42 Since either mild AWD or straw return increased N2O, it is difficult to directly conclude they are promising agronomic measures to reduce greenhouse effect.
L36-39 “mild AWD irrigation reduced N uptake by rice in the soil and rice aboveground biomass” This is also difficult to directly see the difference from either Fig. 4 or others. We can see adding either urea or straw increased N from N inputs instead of soil, but the difference between CF and AWD should be better presented.
In addition, the description of results was hard to follow. The authors compared their treatments of CK, S, U, U+S in all their figures and tables, but the main conclusion of this experiment was the effects of mild AWD irrigation, so the comparison between CF and mild AWD was often missing for statistics either in the figures or tables.
Finally, language needs improvement throughout the manuscript. For example, nitrogen can be replaced by N after first-time mentioning.
Minor points:
In Abstract, the description of treatments was missing.
L33 Numbers of percentage increase are needed here
L57 reduce water waste and environmental pollution
L65-67 Possible reasons to explain can be introduced here.
L70-72 It seems the balance between CH4 and N2O should emphasized.
L78-81 Way too long containing two which
L95-98 Combine or rephrase the purpose of this study.
L98-101 The hypotheses lack connection between each other
L103-107 2.1 can be combined with 2.2
L184 It is not one-way ANOVA in Table 2, which is three factors instead.
Fig. 1 legend font is too large
L198-202 The difference is dependent on treatments which needs to be specific.
L252-253 No direct evidence is from this experiment in the perspective of microorganisms.
L401-402 Correct “mild AWD irrigation…under mild AWD irrigation”
Kaikuo Wu et al.
Kaikuo Wu et al.
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