Foliar application of magnesium mitigates soil acidity stress in wheat

Soil acidity is one of the most important soil constraints for wheat growth, and magnesium (Mg) can play a critical role in mitigating the adverse effects of soil acidity on plants. There is, however, limited information available about the influence of Mg nutrition, especially foliar application, on wheat (Triticum aestivum) growth in acidic soil. In a series of glasshouse experiments, Al-sensitive wheat genotype (ES8) was grown to vegetative stage (Zadoks 23) with or without foliar Mg application at different rates (0, 50, 200 and 1,000 mg Mg/L), and acidic soil was used as the growth medium with or without lime and Mg amendment. The effects of these treatments on plant growth, physiological responses, tissue concentration of Mg, dry biomass accumulation and root length were characterized. Magnesium application to foliage significantly increased (by around 14%) both shoot and root dry biomass compared to the control (0 foliar Mg). No significant variation was observed in response to different Mg salts (sulphate or chloride) applied to either soil or foliage in relation to wheat growth and physiological responses. Other than liming, foliar Mg application (200 mg Mg/L) coupled with Mg application to soil (20 mg/kg soil) provided optimum conditions for wheat growth in an acid soil. Leaf extension rate, chlorophyll content and root length of wheat treated with 200 mg Mg/L foliar application were increased significantly (by 12%, 10% and 23%, respectively) in comparison to plants treated with 0 foliar Mg. Physiological parameters such as net photosynthetic rate, transpiration rate and stomatal conductance were 4-fold higher in foliar Mg-treated plants compared with those receiving no foliar Mg. Therefore, applying 200 mg Mg/L to the foliage may assist in minimizing the negative impact of soil acidity on wheat growth.