Calcium silicate-mediated amelioration of aluminium toxicity in wheat

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Background and aims Soil acidity and aluminium toxicity cause significant yield losses in wheat. Silicon may help ameliorate aluminium toxicity by increasing the soil pH and production of root exudates, or by forming aluminium–silicon complexes. This pot study with wheat aimed to identify a suitable source and rate of silicon optimal for root and shoot growth, characterise the impact of silicon on aluminium toxicity in acidic soil, and explore the potential underlying mechanisms. Methods In the first experiment, wheat breeding line ES8 was grown in pots with acidic soil amended with two silicon sources (Ca or Na silicate) at five rates. In the second experiment, two near-isogenic wheat lines were grown in soils treated with Ca silicate (0, 0.2 and 0.5 g Si kg −1 soil) or Ca carbonate (the same amount of Ca as in 0.2 and 0.5 g Si kg −1 ). Results Calcium silicate increased shoot and root dry weights, root length, photosynthetic parameters, shoot Si concentration and soil pH CaC12 , whereas it decreased Al concentration in shoots of both near-isogenic wheat breeding lines. There were no differences in organic acid anion exudation among the treatments, but Ca silicate decreased the GEOCHEM-EZ-derived relative proportion of free Al and increased that of Al–OH species in both topsoil and subsoil. Conclusions Calcium silicate improved shoot and root growth of wheat in Al-toxic soil, which was associated with a decreased proportion of free Al in the soil solution. Hence, Ca silicate can be an additional measure for ameliorating Al toxicity in soil.