Essential oil yield and yield components of basil (Ocimum basilicum L.) as affected by genotype and intrarow spacing at Jimma, SW Ethiopia

Basil is an aromatic, medicinal, culinary, and multifunctional herb which is grown in different parts of Ethiopia. Although the oil distilled from the herb, as well as its herbal yields, are a crucial input in the pharmaceutical industry and for culinary purposes, the yield obtained is below its potential due to various challenges. Genotype and plant spacing are two of the factors which contribute to the low production of the crop. A field trial was conducted at Jimma University College of Agriculture and Veterinary Medicine (JUCAVM) in 2016 and 2017 to assess the effect of genotype and plant spacing on essential oil yield and other yield-related traits of this important herb. Four promising genotypes (BO-1, BO-3, BO-4, and BO-5) and three plant spacings (20, 30, and 40 cm) were studied in a 4 × 3 factorial design arranged as randomized complete blocks (RCBD) with three replications. Data on plant height, leaf area, number of primary branches, essential oil content and oil yield were collected and analyzed. The analysis of variance revealed that there were highly significant (p < 0.01) interaction effect of genotype with plant spacing for all parameters tested. The maximum essential oil yield (7.88 kg ha−1) was obtained from genotype BO-5 at 30 cm spacing, whilst the least (2.68 kg ha−1) was recorded from BO-1 at 40 cm spacing. The maximum oil content (101 mL g−1) was gained from BO-1 at 20 cm, but BO-3 at 30 cm spacing recorded the least oil content though there were no significant differences between the three treatment combinations. Further studies at different locations and seasons will be important to for future local recommendations.