PubMed · 2026-06-03
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.
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.
