Abstract
Abstract: The objective of this work was to evaluate the effect of magnesium foliar spray on yield performance of soybean (Glycine max) and corn (Zea mays) cultivated in soil with adequate levels of base saturation and magnesium content in Brazil. The field trials were conducted on a Typic Hapludox cultivated with soybean and corn in the 2013/2014 and 2014/2015 crop seasons, respectively. Treatments consisted of Mg rates (50, 100, 250, 500, 1,000 and 1,500 g ha-1 and a control without Mg) applied during the V4, R1, and R5.1 (soybean) or V4 and R2 (corn) phenological growth stages as magnesium sulfate heptahydrate (MgSO4∙7H2O). The SPAD index, leaf Mg content, grain yield, and 100-grain weight were evaluated. The Mg foliar spray increased the SPAD index in soybean and the leaf Mg content in corn. The Mg rates of 540 and 890 g ha-1 increased in 325 and 737 kg ha-1 the yield performance of soybean and corn, respectively, regardless of the phenological growth stages. The Mg application during the reproductive stages increased in 2% the 100-grain weight for both crops. Foliar spraying of Mg improves the yield performance in soybean and corn crops.
Highlights
Magnesium is an essential element to plants, being a constituent of the chlorophyll molecule and acting in phosphorylation, translocation of photoassimilates and in the activation of multiple enzymes, such as glutathione synthetase and phosphoenolpyruvate (PEP) carboxylase
The Mg source used for the foliar fertilization was magnesium sulfate heptahydrate (MgSO4∙7H2O containing 9% Mg), which was applied in solution at a spray rate of 300 L ha-1 using a CO2-pressurized sprayer
The Mg foliar spray increased the SPAD index linearly with increases in the Mg rate (Table 2). This result can be explained by the increase in chlorophyll, since magnesium is the center of the molecule
Summary
Magnesium is an essential element to plants, being a constituent of the chlorophyll molecule and acting in phosphorylation, translocation of photoassimilates and in the activation of multiple enzymes, such as glutathione synthetase and phosphoenolpyruvate (PEP) carboxylase. Even in soils with adequate Mg levels, Mg deficiency may occur due to excessive acidity, high levels of aluminium or manganese, salinity, low water availability in the soil, and low plant transpiration (Mengel & Kirby, 2001; Lynch & St. Clair, 2004; Gransee & Führs, 2013). High levels of Mg in the soil can inhibit the absorption of zinc and Mn causing the deficiency of these elements (Moreira et al, 2003). Fertilization with high potassium levels can result in Mg deficiency once K inhibits Mg absorption by plants (Guiet-Bara et al, 2007)
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