The combined effects of plant density, chitosan, and amino acids enhance the sunflower growth and yield under water deficit conditions

Abstract

Integrating plant density management with chitosan and amino acid-based biostimulant represents a promising strategy to enhance crop performance under water-limited conditions. In this study, we evaluated the combined effects of plant density, foliar chitosan, and amino acid-based biostimulant on sunflower growth, morphophysiological traits, and yield under water deficit conditions. A field experiment was conducted using a split-split-plot design with four replicates, where plant density (25,000 and 50,000 plants ha⁻¹) was assigned to the main plots, chitosan application (0 and 200 mg L⁻¹) to the subplots, and amino acid-based biostimulant (0 and 1.2 mL L⁻¹ as VIUSID^® Agro) to the sub-subplots. Our results indicated that increasing plant density from 25,000 to 50,000 plants ha⁻¹ significantly enhanced crop performance under water-deficit conditions, improving growth indices and seed yield. The combined treatment D_50,000Q₂₀₀A_1.2 (50,000 plants ha⁻¹ + 200 mg L⁻¹ chitosan + 1.2 mL L⁻¹ amino acids) produced the strongest responses and the highest seed yield when compared with D_25,000Q₀A₀ (25,000 plants ha⁻¹ without chitosan or amino acid application). Specifically, D_50,000Q₂₀₀A_1.2 increased plant height by 66%–70%, leaf area by 56%–71%, leaf area index by 111%–127%, dry biomass by 92%–169%, and relative chlorophyll content by 39%–47%, indicating enhanced photosynthetic capacity under water-deficit conditions. These improvements translated into substantial yield gains, with seed yield increasing by up to 3.1-fold relative to the D_25,000Q₀A₀ treatment. Overall, these findings demonstrated that the synergistic integration of optimized plant density with foliar chitosan and amino acid biostimulants enhances sunflower growth, physiological performance, and productivity under water-deficit conditions, providing a robust and sustainable strategy for improving crop resilience and yield stability.

Keywords

amino acid biostimulants / chlorophyll content / crop growth rate / drought tolerance / morphophysiological traits / photosynthetic efficiency

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