Limited irradiance, artificial fluorescent irradiance, and nitrate-N:ammonium-N impact on biomass and essential oil production of Ocimum basilicum L.

In the United States, there is an increasing trend in consumer participation in herb gardening. One of the more popular herbs available, basil (Ocimum basilicum L.) is a culinary herb with a wide variety of uses and cultivars. With an increased need to support the growing demand for herbs, it is important to understand how various growing practices impact basil production. In particular, this research investigates several aspects of growing basil, including how limited irradiance, artificial fluorescent irradiance, and nitrate-N:ammonium-N fertilizer influences growth and essential oil production. In our limited irradiance study, ‘Genovese’ basil plants were grown in a greenhouse under shade structures that provided 0%, 30%, 50%, or 70% shade. Basil fresh weight and shoot indices increased as percent shade decreased. Essential oil peak areas were predicted to be the greatest for eucalyptol at 60% shade, linalool at 30% shade, and eugenol at 40% shade. Irradiance intensity is typically suboptimal for growing plants indoors. Fluorescent lighting systems are recommended for supplemental lighting in a residential setting. In our study with basil, it was found that plants grown under fluorescent grow lamps tended to have higher shoot indices and higher fresh weight compared with plants grown under cool white fluorescent lamps; yet no differences were found in essential oil content among lighting systems tested. Nitrate and ammonium forms of N are commonly used to fertilize plants. Different nitrate-N:ammonium-N treatments were tested with basil plants, which included 0:100, 25:75, 50:50, and 75:25 and a non-fertilized control to compare plant growth and essential oil content. Basil plants grown with a nitrate-N:ammonium-N of 75:25 tended to have the highest fresh weights compared to other fertility treatments, whereas the 50:50 treatment tended to have the highest shoot indices. The 75:25 nitrate-N:ammonium-N treatment tended to have greater linalool, eucalyptol, and eugenol compared to other ratio treatments. Based on our results, basil appears to have greater fresh weight and essential oil production when grown with a 75:25 ratio of nitrate-N:ammonium-N