Addition of wheat straw to acid sulfate soils with different clay contents reduces acidification in two consecutive submerged-moist cycles

•Wheat straw addition reduced acidification under oxidizing conditions.•Under submerged conditions, wheat straw addition promoted pH increase and reduced redox potential.•Effect of wheat straw on pH was greater in soils with low clay content (10%, 15%) than clay-richer soils (23% and 38%)•Amendment effects still evident after two submerged-moist periods (2 × 12 weeks)