Growth and Oil Production of Fennel (Foeniculum vulgare Mill): Effect of Irrigation and Organic Fertilization

Abstract

ABSTRACT Seeds of the aromatic plant fennel (Foeniculum vulgare Mill) were sown in sandy soil with 0 or 2.5 kg m−2 of organic fertilizer (OF); chicken manure, cattle manure or plant compost. Plants were irrigated two, three, four, five or six times at 21-day intervals commencing 21 days after sowing and continuing until harvest. Increasing the number of irrigations and application of organic fertilizers significantly delayed harvesting. Water stress imposed by restricting the number of irrigations significantly decreased plant height, branch number, and fruit and oil yield, whereas it increased the percentage volatile oils. All organic fertilizers increased plant growth and yield parameters. With or without organic fertilization, the increase in fruit yield with irrigation outweighed the decrease in volatile oil percentage, so volatile oil yield increased with irrigation. However, there was no significant difference in volatile oil yield between five and six times irrigated plants under any type of fertilization. By increasing both fruit yield and volatile oil percentage, organic fertilizers considerably increased oil yield. Chicken manure fertilized plants irrigated five or six times gave the highest volatile oil yields of 2.08 and 2.09 ml plant−1, respectively, followed by cattle manure fertilized plants irrigated five times (1.98 ml plant−1).