Effect of water regime and harvest stage on essential oil accumulation in basil plant growing in sandy soil

Abstract

Basil (Ocimum basilicum.L) is an aromatic herb with economic importance due to its essential oils useful for the production of foods, perfumes, and medicines. Its chemical composition may vary by genetic factors, harvesting stage, and water availability. This work evaluated the content, yield, and the composition of sweet basil essential oil irrigated at different levels of soil water tension and harvested at different flowering stages. Plants were grown in 14-L pots inside a greenhouse located at the Sao Paulo State University (UNESP), Brazil. The 15 treatments were the combination of 5 levels of soil water tension that define when to irrigate (20, 30, 40, 50, and 60 kPa) with 3 harvest stages (beginning of flowering, full flowering, and end of flowering). Growth traits including total dry and fresh mass per plant and inflorescences, plant height, stem diameter, and inflorescences number were highest in plants grown at lower soil water tensions, 20 and 30 kPa. The harvesting at the end of flowering generated the highest values of essential oil content and yield. The 60 kPa soil water tension showed the highest percentage of essential oil content in dry mass, indicating that water stress concentrated essential oil in the plant. However, the basil profit is a function of the essential oil yield. The highest essential oil yield (g, dry weight basis) occurred when irrigation started at 20 and 30 kPa. The chemical components of the essential oil showed low variation, regardless of the treatment. For all the treatments, linalool was the components found in a more considerable amount, and its highest accumulation occurred when irrigated at soil water tension of 20 kPa and 30 kPa. A useful recommendation for basil growers is irrigation scheduling with 30 kPa and harvest at the end of flowering.