DOI: 10.57760/sciencedb.10897
title: Variation of the Increased CH4 Emissions in Paddy Fields with Straw Incorporation across 11 Consecutive Years
title: 连续11年不同秸秆还田量下稻田甲烷增排效应变化研究

description: This study aimed to explore the variations of the increased methane (CH4) emissions and its mechanisms in paddy fields with straw incorporation across 11 consecutive years, so as to provide a scientific basis for the accurate assessment of CH4 emissions under long-term straw incorporation.【Method】A typical double-cropping rice field in the subtropical region was selected as the research subject, and the fertilizer only treatment (CON), low amount of straw incorporation treatment (3.0 t·hm-2, LS) and high amount of straw incorporation treatment (6.0 t·hm-2, HS) were set up. The field experiment was conducted for 11 years (2012—2022) with CH4 fluxes and related soil and environmental factors measured in the early and late rice seasons across the 11 years.【Result】The results showed that in the 11th year of straw incorporation, CH4 emissions in both the LS and HS treatments were substantially higher than those in the CON treatment, with the highest emissions recorded in the HS treatment, followed by the LS and then the CON treatment (HS &gt; LS &gt; CON). However, it was noted that the increment in CH4 emissions due to straw incorporation in the 11th year had diminished by 75.1% and 83.5% when compared to the increment in the first year (P &lt; 0.05). In the 11th year, the contents of soil organic carbon (SOC), ammonium nitrogen (NH4+-N), and dissolved organic carbon (DOC) in the LS and HS treatments showed significant increases by 7.90% and 20.8% (LS and HS treatments, the same as below), and 15.0% and 25.7%, 19.5%, and 31.3%, respectively, compared to the CON treatment (P &lt; 0.05). However, the redox potential (Eh) and soil bulk density (BD) exhibited significant reductions of 14.1% and 21.7%, and 10.3% and 7.76%, respectively (P &lt; 0.05). Furthermore, the abundance of the mcrA and pmoA genes, which are instrumental in methanogenesis and methane oxidation processes, respectively, as well as the mcrA/pmoA gene ratio, were significantly enhanced in the LS and HS treatments compared to the CON, which increased by 96.0% and 152%, 12.7% and 34.8%, and 73.9% and 85.8%, respectively (P &lt; 0.05). Through redundancy analysis, it was determined that in the 11th year of straw incorporation, CH4 emissions in the paddy field displayed a significant positive correlation with the abundance of mcrA and the mcrA/pmoA ratio in the soil (P &lt; 0.05). The decrease in BD and the rise in Eh, induced by the increase in SOC content, likely fostered the augmentation in pmoA gene abundance, which might be the principal reason for the undermined increase in CH4 emissions for the straw treatments observed in the later stages of the experiment.【Conclusion】 In the subtropical regions, relative to CON, the increases in CH4 emissions under long-term straw incorporation was reduced by approximately 80% (P &lt; 0.05) compared to the increase under short-term straw incorporation due to the changes in SOC, BD, and Eh. Therefore, the assessment of CH4 emissions from paddy fields with straw incorporation needs to be dynamically adjusted according to the year of duration of straw incorporation.
description: This study aimed to explore the variations of the increased methane (CH4) emissions and its mechanisms in paddy fields with straw incorporation across 11 consecutive years, so as to provide a scientific basis for the accurate assessment of CH4 emissions under long-term straw incorporation.【Method】A typical double-cropping rice field in the subtropical region was selected as the research subject, and the fertilizer only treatment (CON), low amount of straw incorporation treatment (3.0 t·hm-2, LS) and high amount of straw incorporation treatment (6.0 t·hm-2, HS) were set up. The field experiment was conducted for 11 years (2012—2022) with CH4 fluxes and related soil and environmental factors measured in the early and late rice seasons across the 11 years.【Result】The results showed that in the 11th year of straw incorporation, CH4 emissions in both the LS and HS treatments were substantially higher than those in the CON treatment, with the highest emissions recorded in the HS treatment, followed by the LS and then the CON treatment (HS &gt; LS &gt; CON). However, it was noted that the increment in CH4 emissions due to straw incorporation in the 11th year had diminished by 75.1% and 83.5% when compared to the increment in the first year (P &lt; 0.05). In the 11th year, the contents of soil organic carbon (SOC), ammonium nitrogen (NH4+-N), and dissolved organic carbon (DOC) in the LS and HS treatments showed significant increases by 7.90% and 20.8% (LS and HS treatments, the same as below), and 15.0% and 25.7%, 19.5%, and 31.3%, respectively, compared to the CON treatment (P &lt; 0.05). However, the redox potential (Eh) and soil bulk density (BD) exhibited significant reductions of 14.1% and 21.7%, and 10.3% and 7.76%, respectively (P &lt; 0.05). Furthermore, the abundance of the mcrA and pmoA genes, which are instrumental in methanogenesis and methane oxidation processes, respectively, as well as the mcrA/pmoA gene ratio, were significantly enhanced in the LS and HS treatments compared to the CON, which increased by 96.0% and 152%, 12.7% and 34.8%, and 73.9% and 85.8%, respectively (P &lt; 0.05). Through redundancy analysis, it was determined that in the 11th year of straw incorporation, CH4 emissions in the paddy field displayed a significant positive correlation with the abundance of mcrA and the mcrA/pmoA ratio in the soil (P &lt; 0.05). The decrease in BD and the rise in Eh, induced by the increase in SOC content, likely fostered the augmentation in pmoA gene abundance, which might be the principal reason for the undermined increase in CH4 emissions for the straw treatments observed in the later stages of the experiment.【Conclusion】 In the subtropical regions, relative to CON, the increases in CH4 emissions under long-term straw incorporation was reduced by approximately 80% (P &lt; 0.05) compared to the increase under short-term straw incorporation due to the changes in SOC, BD, and Eh. Therefore, the assessment of CH4 emissions from paddy fields with straw incorporation needs to be dynamically adjusted according to the year of duration of straw incorporation.