Ferrous Iron Addition Decreases Methane Emissions Induced by Rice Straw in Flooded Paddy Soils,ACS Earth and Space Chemistry

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Ferrous Iron Addition Decreases Methane Emissions Induced by Rice Straw in Flooded Paddy Soils
ACS Earth and Space Chemistry ( IF 3.4 ) Pub Date : 2020-05-11 , DOI: 10.1021/acsearthspacechem.0c00024
Jinli Hu _{1,

2} , Hongtao Wu _{1,

2,

3} , Zheng Sun _{1,

2,

4,

5} , Qi-an Peng ₆ , Jinsong Zhao _{1,

2} , Ronggui Hu _{1,

2}

Affiliation

Straw returning to fields is a common agricultural practice for enhancing soil fertility and organic matter, although it induces substantial CH₄ emissions from flooded paddy soils. The characteristics of long-term periodic management of irrigation and drainage intensely affect the redox cycling of iron in paddy soil and could be one of the major factors regulating CH₄ production. Currently, this regulatory effect is rarely applied to CH₄ mitigation during straw returning to fields. To clarify the influences of iron on CH₄ emissions induced by straw incorporation, an laboratory incubation experiment was conducted with the addition of rice straw and two different concentration levels of ferrous iron (3.7 and 7.4 g of Fe²⁺ kg^–1 of soil) to two paddy soils (collected from Luotian, Hubei Province, and Changsha, Hunan Province, China, hereafter called LT and CS soils, respectively). Our result showed that CH₄ emissions from straw addition treatment were 125.4 and 45.5 times greater than the amount without straw addition in LT and CS soils, respectively. Fe²⁺ addition significantly decreased CH₄ emissions induced by rice straw by over 50% in both soil samples. Moreover, the stimulation of straw on CH₄ emission was almost offset by twice the content of Fe²⁺ amendment in LT soil. Fe²⁺ addition significantly decreased the dissolved organic carbon (DOC) content, with 21–39% in LT soil and 31–42% in CS soil, compared to the straw addition treatment. The Fe(II) accumulation rate, microbial biomass carbon content, and CO₂ emissions were also suppressed by Fe²⁺ addition. These results indicate that the addition of Fe²⁺ suppressed the reduction of Fe(III) to Fe(II), leading to less DOC release from Fe–organic matter associations. The microbial activity and biomass could be influenced by the DOC availability, leading to further inhibition of CH₄ emissions. Our result implies that Fe-rich soils may be more suitable for returning straw, and further research about methanogens and methanotrophs is needed.

更新日期：2020-06-18

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