Effect of exogenous proline application on yield and yield components of second-crop maize under water deficit conditions

Abstract

Water scarcity is a major constraint limiting maize productivity in arid and semi-arid regions. This study evaluated the effects of exogenous proline application on yield, yield components, and water productivity of second-crop maize under different irrigation levels. The field experiment was conducted at Harran University, Şanlıurfa, Türkiye, using a split-plot design in randomized complete blocks with three replications. Irrigation levels consisted of 100% (IW1), 75% (IW2), and 50% (IW3) of full irrigation, while proline (Pro) treatments included a control and 1 mM exogenous proline. Increasing water deficit reduced plant height, cob length, cob diameter, thousand-grain weight, hectoliter weight, and grain yield. However, proline application improved most traits, particularly under deficit irrigation. Compared with the control, proline increased grain yield by 3.53%, 41.05%, and 43.98% under IW1, IW2, and IW3, respectively. Seasonal irrigation water ranged from 392 to 723 mm, while seasonal crop evapotranspiration varied between 411 and 731 mm. The highest irrigation water productivity (1.77 kg m⁻³) and water productivity (1.70 kg m⁻³) were obtained from the Pro-IW2 treatment. Principal component analysis showed a clear separation of treatments according to irrigation level and proline application. As a result, 1 mM exogenous proline application may be a promising approach for improving yield performance and water productivity of second-crop maize under semi-arid conditions.