Gibberellic and salicylic acids improve seedling emergence, early growth and some physiological characteristics of Phaseolus vulgaris L. under soil compaction

Abstract

Heavy soil compaction and crusting adversely affect the percentage and speed of seedling emergence, particularly in dicotyledonous epigeal plants. This study aimed to evaluate ways to cope with this phenomenon in kidney bean through hormonal priming. A factorial experiment was conducted based on a completely randomised design with three replications. The factors were seed priming (control, hydropriming, gibberellic acid 50 mg kg⁻¹ (GA 50), GA 100, salicylic acid 50 mg kg⁻¹ (SA 50), SA 100 and GA 50 + SA 50) and soil compaction (bulk density 1 340, 1 410, 1 470, 1 540 and 1 610 kg m^–3). Results showed that soil compaction decreased root length and increased root branches. The longest root was observed following priming with GA 50 + SA 50 and no soil compaction (intact soil). Seed priming significantly affected seedling emergence and early growth indices. Priming improved root length and the number of root branches, while soil compaction suppressed root length and increased the number of root branches. Seed priming also significantly affected chlorophyll a, carotenoid, catalase and superoxide dismutase levels. Superoxide dismutase and catalase activities were increased by soil compaction, especially at 15% and 20% soil bulk density (ρ) (ρ = 1 540 and 1 610 kg m⁻³). In general, mild soil compaction (5% or ρ = 1 410 kg m⁻³) accelerated seedling emergence and improved growth. However, increased soil compaction by 15% or more, decreased root and shoot growth. Hydropriming decreased seedling emergence under soil compaction, and was unsuitable for such conditions. Combined hormonal priming (GA 50 + SA 50) was the best treatment for seed resilience to soil compaction.