Statistical Assessment of the Superiority of Agro-Climatic Zones for Sandalwood (Santalum album L.) Cultivation Based on Variability in Tree Growth and Soil Fertility Parameters in Karnataka, India

Sandalwood (Santalum album L.), a highly valued aromatic tree species, is renowned for its heartwood, which is rich in essential oils used in perfumes, cosmetics, and traditional medicine. In India, Karnataka is a major hub for sandalwood cultivation, owing to its diverse agro-climatic conditions and historical significance in sandalwood trade. This study aimed to statistically evaluate the suitability of nine Agro-Climatic Zones (ACZs) for optimal sandalwood cultivation by analyzing variability in soil fertility and tree growth parameters across 73 taluks. Data were collected on key soil properties—pH, electrical conductivity (EC), organic carbon, macro- and micronutrients—as well as tree parameters such as age, height, diameter, heartwood content, and heartwood diameter. Rainfall across taluks ranged from 266.5 to 1376.4 mm (mean: 471 mm, CV: 56.9%), and mean annual temperatures varied between 23.7°C and 28.0°C (mean: 25.2°C, CV: 4.4%). Tree ages ranged from 9.5 to 11.5 years across zones. Soil pH varied from 6.53 to 7.31, while EC ranged from 0.06 to 0.39 dS/m. Substantial variability was observed in nutrient concentrations: nitrogen (127.35–402.77 kg/ha), phosphorus (18.68–39.20 kg/ha), potassium (300.4–661.08 kg/ha), calcium (1428.38–8078.47 ppm), and micronutrients including Fe, Mn, Zn, and Cu. Statistical comparisons (Student’s t -test) revealed significant differences in tree diameter, heartwood diameter, and heartwood percentage among specific ACZs. No significant variation was observed in tree height. Ranking of zones based on tree performance (RS1), soil pH and EC (RS2), macro-nutrients (RS3), and micro-nutrients (RS4) indicated that ACZ-3 ranked highest overall (rank sum: 69), followed by ACZ-8 (rank sum: 75). Notably, ACZ-6 and ACZ-9 also demonstrated superior performance for selected parameters. These findings underscore the influence of soil fertility and agro-climatic conditions on sandalwood growth and heartwood formation. The results are valuable for identifying site-specific strategies for sandalwood plantation development and improving heartwood yield under similar environmental conditions. These findings highlight ACZ-3 and ACZ-8 as optimal for sandalwood cultivation, with ACZ-6 excelling in heartwood production, guiding zone-specific management for maximizing growth and heartwood yield.