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.

罗勒（罗勒罗勒.L）是一种具有经济重要性的芳香植物，因为其精油可用于食品，香料和药物的生产。其化学成分可能因遗传因素，收获阶段和水的可用性而异。这项工作评估了在不同土壤水分张力下灌溉并在不同开花阶段收获的甜罗勒精油的含量，产量和组成。将植物种植在位于巴西圣保罗州立大学（UNESP）的温室内的14升盆中。这15种处理方法是5种土壤水分张力的组合，它们定义了何时进行灌溉（20、30、40、50和60 kPa）以及3个收获阶段（开花开始，完全开花和开花结束）。生长性状，包括每株植物和花序的总干燥和新鲜质量，植物高度，茎直径，在较低的土壤水分张力（20和30 kPa）下生长的植物的花序和花序数最高。开花结束时收获的香精油含量和产量最高。60 kPa的土壤水分张力显示干物质中精油含量最高，表明水分胁迫使植物中的精油集中。然而，罗勒的利润是精油产量的函数。当以20和30 kPa开始灌溉时，香精油的最高产量（以干重为基础）出现了。不论处理如何，精油的化学成分均显示出较低的变化。在所有处理中，芳樟醇的含量均较高，在土壤水分为20 kPa和30 kPa的条件下灌溉时，其积累量最高。