TITLE:
Effects of KNO3 on Germination Rate and Seedling Vigor of Macadamia Seeds in Morogoro, Tanzania
AUTHORS:
Mariam Nyasasi, Richard Madege, Beatrice Mwaipopo
KEYWORDS:
Macadamia integrifolia, Potassium Nitrate, Seed Germination, Seedling Vigor
JOURNAL NAME:
Open Access Library Journal,
Vol.12 No.9,
September
19,
2025
ABSTRACT: This study evaluated the effects of potassium nitrate (KNO₃) priming on the germination and early seedling development of macadamia (Macadamia integrifolia) seeds. Four KNO3 concentrations—0.19 M (C1), 0.25 M (C2), 0.40 M (C3), and a control (0 M, C4)—were tested in a completely randomized design with three replications. Data collected included germination percentage (GM), number of normal and abnormal seedlings (NS, ABS), seedling vigor index (SVI), and seedling growth parameters such as shoot and root height, growth rates, biomass, and stem/root girth. Statistical analysis was conducted using analysis of variance (ANOVA) in Origin Pro 2024 (Origin Lab Corporation) and R version 4.4.2 (R Core Team, R Foundation for Statistical Computing). Results showed that germination percentage was not significantly affected across treatments (p = 0.4); however, KNO3 concentration significantly influenced the number of normal seedlings (p = 0.01), abnormal seedlings (p = 0.03), and seedling vigor index (p = 0.00025). The highest vigor and lowest abnormality rates were observed in C1 and C4, while the highest abnormality (10%) and lowest vigor occurred in C3, indicating that excessive nitrate concentrations may induce stress. No significant differences (p > 0.05) were found in shoot and root elongation, biomass, or tissue girth, suggesting that while KNO3 influences early metabolic and physiological activation, it does not significantly alter short-term morphological growth parameters. Principal Component Analysis (PCA) revealed that SVI, shoot growth rate (SGR), and root growth rate (RGR) were key contributors to early seedling vigor, with C1 and C4 treatments aligning positively along the principal component associated with vigorous growth. These findings support the use of moderate KNO₃ concentrations to enhance seedling vigor and quality in macadamia, while highlighting the importance of avoiding excessive nitrate levels that may compromise seedling development.