Unravelling the Influence of Various Salinity Sources on the Biochemical and Physiological Traits and N Use Efficiency of Maize (Zea mays L.)

Abstract

Among abiotic factors, salinity is causing increasingly devastating consequences for crop growth and productivity as it expands globally. The yield of crops is reliant on the types of salts, their severity and the type of plant—whether it is a glycophyte or halophyte—because various salts are present in ionic forms in salt-affected soils. These diverse salts, whether occurring alone or in combination, exert varying effects on plant physiology and the plant's tolerance mechanisms. To comprehensively understand the comparative influences of different salt sources on the physiological and biochemical traits of maize, which are relatively sensitive to salinity, it is essential to examine their threshold levels under saline conditions. A pot experiment was conducted under saline conditions using two different salts, NaCl and Na₂SO₄, applied individually and in combination (NaCl + Na₂SO₄) at a 1:1 ratio across five salinity levels: 0, 7, 10, 13 and 16 dS m⁻¹, including a control that remained untreated. The results depicted that the parameters regarding physiological attributes (relative water contents [RWC], electrolyte leakage [EL] and membrane stability index [MSI]), biochemical attributes (proline and malondialdehyde [MDA]), antioxidant enzymes (catalase [CAT], peroxidase [POD] and superoxide dismutase [SOD]) and N use efficiencies (N use efficiency [NUE], physiological N efficiency [PNE], N yield efficiency [NYE], N harvest index [NHI] and photosynthetic N use efficiency [PNUE]) of maize were affected negatively by increasing the concentrations of salts. However, the severity of these effects was highly pronounced with NaCl at all concentrations from 7 to 16 dSm⁻¹ of salinity stress as compared to Na₂SO₄ and their mixtures. This is primarily due to the buildup of Na⁺ and Cl⁻ ions in high concentrations, particularly at 16 dS m⁻¹. The outcomes highlight the significance of managing naturally existing salt sources in soils worldwide to alleviate their damaging effects on maize cultivation and to enhance crop resilience and productivity.