Response of Growth, Yield and Essential Oil of Geranium Plants to Surface Irrigation and Humic Acid Treatments

Water is among the most important factors affected growth, yield and quality of medicinal and aromatic plants since its deficiency may cause serious growth harms and yield losses. Egypt suffers from a scarcity of water, so each drop should be preserved. Therefore, the objective of the present study was to determine the suitable irrigation treatment (120, 100 and 80% ETo (evapotranspiration) and humic acid amounts (control), 1.0, 1.5 and 2.0 cm/L) that attain the highest growth, yield and essential oil of geranium (Pelargonium graveolens L. Herit Aiton) under surface irrigation in clay soil at El Kanater El Khairiya. Results showed that humic acid alleviated the deteriorative effect of water deficiency, where plants irrigated with 120% ETo and treated with 2.0 cm/L humic acid improved the growth characters in terms of plant height, number of branches, fresh, dry weights and volatile oil yield. While, the highest volatile oil percentage and proline content were recorded at 80% ETo with humic acid at 2.0 cm/L treatment during the two growing seasons. Results also showed that the applied irrigation water under 120% ETo treatment was 7192 m3/fed averaged over the two growing seasons attained the highest yield. The highest values of water use efficiency and water productivity were 14.1 and 10.0 averaged over the two growing seasons attained under 80% ETo and application of 2.0 cm/L humic acid. Thus, it can be concluded that the required irrigation water for geranium is under 120% ETo. However, under water deficiency, 80% ETo and 2.0 cm/L humic acid could be applied, which increase geranium yield by 24%, compared to the 120% ETo treatment averaged over the two growing seasons.