The effect of nitrogen and phosphorus on growth, yield of flowers and essential oil of chamomile (matricaria chamomilla l.) grown under Kenya conditions
An experiment was carried out at the Field Station, University of Nairobi, Kabete Campus to find out firstly, the effect of nitrogen, (0, 50, 100 and 150 kg N/ha) and phosphorus (0, 17.47, 34i93 and 52.41 kg P/ha) rates, and their interaction on growth, flower and essential oil yields and quality of chamomile plants; and secondly whether chamomile plants can grow under Kenyan conditions and at an altitude above 1800 m above sea level. The treatments were laid down in a split-plot design with three replicates. The variety Max et Oljea was used. The essential oil was extracted by steam distillation using Clevinger apparatus and its composition was determined by gas liquid chromatography. The results showed that vegetative growth and dry matter production of chamomile plants were significantly increased by nitrogen application. Nitrogen at 50 kg Nlha increased significantly both fresh and dry flower yields of the plants. Increasing nitrogen application from 0 to 100 kg N/ha, increased essential oil yield per unit dry flower weight and per plant from 0.627 to 1.036% and from 5.85 to 16.64 kg/ha., respectively. However, application of more than 50 kg N/ha did not significantly increase essential oil yield from the plants. Essential oil yield per unit dry flower weight increased with increasing phosphorus application. Increasing application of phosphorus from 0 to 17.47 kg P/ha. increased essential oil yield from 0.728 to 0.914%. Applying more than 17.47 kg P/ha. decreased the essential oil yield. Increasing application of nitrogen and phosphorus, from 0 to 50 kg N/ha, and 0 to 17.47 kg P/ha. increased chamazulene concentration in the essential oil from 6.89 to 8.60%, and from 7.07 to 8.25%, respectively. However, application of more than 50 kg N/ha and 17.47 kg P/ha. led to a decrease of chamazulene. Nitrogen fertilization significantly decreased bisabololoxides "A" and "B" concentration in the essential oil of chamomile flowers. Increasing application of nitrogen from 0 to 150 kg N/ha. decreased bisabololoxides "A" and "B" concentration in the essential oil from 41.56 to 31.58% and from 21.69 to 13.19%, respectively. Nitrogen fertilization increased farnesene content in the essential oil of chamomile flowers. However, applying more than 50 kg N/ha. increased farnesene concentration. The interactions between nitrogen nad phosphorus, had no significant influence on chamomile plant growth, development, yield and quality of the essential oil. In general, the results showed that nitrogen played a vital role in the growth and development of chamomile plants and in the biosynthesis of the essential oil and its components from the plants. Phosphorus fertilization did not significantly influence the growth and development of the plants. However, it is recommended that further research should be done in the areas of plant nutrition, ecological zones, plant breeding and varietal evaluation, plant biochemistry and the economic evaluation of chamomile growing in Kenya.