Ameliorating Lime-Induced Stress in Arctotis × hybrida through Peat Moss and Perlite Amendments: Growth, Physiology, and Multivariate Analysis

Abstract

This study evaluates how organic and inorganic soil amendments can reduce the negative effects of high pH and low nutrient levels in calcareous soils. The research focuses on improving the growth and quality of Arctotis × hybrida. A randomized complete block design (RCBD) with three replications was used under both indoor and outdoor conditions. Six substrate treatments were tested: 100% calcareous soil (Control, T1), and various mixtures of calcareous soil with either peat moss (25% and 50%; T2, T3) or perlite (25%, 50%, and a mixture; T4, T5, T6). Statistical analysis, including Principal Component Analysis (PCA), showed that the first two components explained 87.4% of the total variance. Peat moss treatments performed significantly better than both the control and perlite-based media. We found a strong negative correlation between soil CaCO3 levels and plant performance (r = -0.65 to -0.82), while growth markers showed strong positive relationships with each other (r > 0.80). Adding peat moss significantly increased leaf area (40.2–48.1%), leaf dry weight (17.8–34.8%), and root dry weight (66.1–165.3%) compared to the control. Additionally, flowering traits improved by up to 47.6%. In contrast, perlite amendments showed only minor benefits. Overall, indoor cultivation produced much better results across all physiological parameters than outdoor environments.