Foliar application of magnesium mitigates soil acidity stress in wheat

Abstract

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.

Genetic aluminium resistance coupled with foliar magnesium application enhances wheat growth in acidic soil

“…This can be interpreted as a consequence of applying Mg to soil in the form of MgSO 4 ·7H 2 O (due to the accompanying sulfate anion) 47 . Although the accompanying ion did not matter in foliar application, 28 it might be different in soil, where sulfate may complex Al in non‐toxic form 48 and contribute to greater shoot growth and Mg content in MgSO 4 ·7H 2 O‐amended plants compared with MgCl 2 ·6H 2 O‐amended plants (Fig. 1(b)).…”

“…A similar response was reported in oregano ( Origanum vulgare ssp. hirtum ) 36 and Al‐sensitive wheat genotype, 28 where the plant growth increased significantly in response to foliar Mg application, when the plants were grown in acidic soil. Similar to Al‐sensitive genotype, applying foliar Mg also increased the growth of Al‐resistant genotype compared with zero foliar‐Mg‐treated plants.…”

“…Two different Mg salts were applied to soil at the same rate to assess whether different anions accompanying Mg would influence the ameliorating Mg effect. In contrast, only MgSO 4 ·7H 2 O was used as a source of foliar Mg, as it has already been demonstrated that the source of Mg is not important when applied to the foliage 28 and MgSO 4 ·7H 2 O is the most commonly used source of Mg for foliar fertilization 29–32 . The amount of limesand (average neutralizing value 95.5%, as listed by the supplier) required to achieve the soil pH of 6.0 for Kalannie subsoil (0.74 g kg −1 ) was determined by the Dunn lime titration method 33 .…”

“…Magnesium can alleviate Al toxicity possibly by improving carbon partitioning, 24 increasing root exudation of organic acid anions, 25 maintaining proton adenosine triphosphatase (H + ‐ATPase) activity 26 and protecting plants from reactive oxygen species 27 . Foliar application of Mg can facilitate wheat growth in acid soil similarly to applying Mg directly to soil; 28 however, this is not practiced widely because of a lack of knowledge about its effectiveness to combat Al 3+ toxicity in acidic soil.…”

Magnesium Foliar Supplementation Increases Grain Yield of Soybean and Maize by Improving Photosynthetic Carbon Metabolism and Antioxidant Metabolism

“…Numerous studies reported the beneficial effect of Mg spraying to relieve environmental stresses in crops, such as drought stress [ 29 ], heat stress [ 20 , 27 ], and soil acidity stress [ 54 ], and temperature [ 30 ] by improving the antioxidant metabolism and reducing the cell damages. During the drought stress, there is a reduction in the use of the energy captured in the photosynthesis reaction centers [ 55 ].…”