Changes in the herb yield, essential oil and some important growth parameters of holly basil (Ocimum sanctum L.) in response to different plant densities and nitrogen levels

Holy basil (Ocimium sanctum L.) is a medicinal and aromatic plant belonging to Lamiaceae family. This study was conducted to determine the most suitable plant density and nitrogen fertilizer rate to improve the qualitative and quantitative traits of Holy basil. The experiment was a randomized complete block design in a factorial arrangement with two factors and four replications. The factors were plant density (D) at 26. 6، 19، 14. 8، and 12. 1 plant per m2، and nitrogen (N) at three levels of 0، 50 and 100 kg/ha. At full flowering stage، plant height، shoot number and length، inflorescence length، fresh and dry weights of shoots and roots، and essential oil content and yield were measured. According to the results، the plant density and nitrogen treatments had significant effects (P≤0. 05) on fresh and dry matter weights، secondary shoot length، essential oil content and yield، and the number of inflorescences. However، the studied treatments did not affect the number of branches، plant height، and root and shoot، root dry matter، chlorophyll content and leaf area. The interaction effects of row spacing and nitrogen levels on all traits with the exception of chlorophyll content and leaf area were significant (P≤0. 05). The highest amounts of fresh and dry matter weights، shoot length، number of inflorescences، essential oil content and yield were obtained in 14. 8 plant per m2 with application of 50 kg N/ha. Essential oil contents (w/w%) varied between 0. 6-1. 1%.