Soil amendments impact hydroxyl radicals production in paddy soil: Dual roles in methane emissions.
Tang Y, Chen N, Peng F, Zeng Y, Wang J
Soil Health
Every bag of lime or compost you work into waterlogged garden beds or rice paddies sets off a chain reaction in the soil chemistry that can tip the ground from absorbing greenhouse gases to releasing them.
Scientists found that common soil improvers—like lime and compost—change how much of a highly reactive molecule (hydroxyl radical) forms in flooded rice paddy soil. That molecule acts like a switch: at low levels it helps break down pollutants and keeps methane in check, but when it builds up past a certain point it actually causes the soil to release more methane, a potent greenhouse gas. The soil amendments raised pH and fed soil microbes, which ultimately pushed conditions past that tipping point and increased methane output.
Key Findings
Low doses of soil amendments (containing CaO and organic matter) increased hydroxyl radical production by 14.9–33.8% compared to unamended paddy soil.
Hydroxyl radicals act as a methane sink below ~701 μmol kg⁻¹ but flip to a methane source above that threshold, demonstrating a concentration-dependent dual role.
Amendments raised soil pH and soil organic carbon, stimulating microbial activity and iron(II) oxidation, which drove the net increase in both hydroxyl radicals and methane emissions.
chevron_right Technical Summary
Adding soil amendments like lime (CaO) and organic matter to rice paddies boosts a powerful natural oxidant called hydroxyl radical, which in turn increases methane emissions from those fields—a finding that complicates the use of soil conditioners in wet agricultural systems.
Abstract Preview
Hydroxyl radicals (•OH) play a critical role in driving contaminants attenuation and elements cycling (e.g., nitrogen cycling) during redox fluctuations of paddy soil. However, such impacts on meth...
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