Effects of irrigation and nitrogen on the yield components of fennel (Foeniculum vulgare Mill.)

Abstract

A field experiment was conducted to study the effects of irrigation and nitrogen applied at different growth stages on the oil and anethole yields of fennel (Foeniculum vulgare Mill.), and its yield components. Irrigation increased the yield of whole plant dry matter, with the stem elongation stage being the most sensitive. Full irrigation and irrigation applied during the flowering and late flowering growth stages increased umbel and oil yields. Irrigation during the late flowering stage made the greatest contribution to oil yield, accounting for >80% of the yield due to full irrigation. This was attributed to the concurrent timing of irrigation during the late flowering stage with dry conditions and the development of the main oil-bearing structures, the secondary and tertiary umbels. Irrigation had no significant effect on the anethole concentration of the oil. The best economic return was achieved by irrigating during the late flowering stage. There was no significant effect of nitrogen on any of the yield components measured in this study.