Fruit yields, essential and fixed oil content, essential oil component and fatty acids profile of fennel in response to different doses of sheep and cow manures

Fennel, a popular aromatic plant from the Apiaceae family, is widely cultivated for its culinary uses. This study investigated the impact of various doses of sheep and cow manure on fennel's growth, yield, and quality during the 2019 and 2020 growing seasons. The research found that specific manure applications significantly influenced fennel's fruit production and desired qualities, while reducing the need for chemical fertilizers and minimizing environmental pollution.

The most productive fennel plants were those treated with 22.5 tons per hectare of cow manure and 22.5 tons per hectare of sheep manure. These applications resulted in the highest fruit yields, at 1.7 tons per hectare and 1.6 tons per hectare, respectively, compared to the control group. The concentrations with the highest essential oil content were 15 tons per hectare of cow manure (26.4 liters per hectare) and 22.5 tons per hectare of sheep manure (25.2 liters per hectare).

The manure doses of 15 tons per hectare and 22.5 tons per hectare of cow manure, and 22.5 tons per hectare of sheep manure, yielded the greatest fixed oil content (21.6%, 19.1%, and 19.1%, respectively). The major chemical components of the essential oils were trans-anethole, limonene, anisaldehyde, and camphor. The manure applications at 22.5 tons per hectare demonstrated the highest trans-anethole content (37.7% for cow manure and 35.9% for sheep manure).

Overall, the findings suggest that utilizing sheep and cow manure as organic fertilizers can yield high-quality fennel fruit while decreasing reliance on chemical fertilizers and reducing environmental pollution. This research is part of the MSc Thesis of first author Furkan Erhan, conducted at the Department of Field Crops, Faculty of Agriculture, Bolu Abant İzzet Baysal University, Bolu, Turkey.