Introduction
Given the diversity of climate and vegetation in Iran, it has provided a great potential for entering the market of medicinal plants and herbal medicines (AmirTeimori et al., 2011). Fennel (Foeniculum vulgare Mill.) is one of the oldest medicinal and spice plants in Iran and the world, which is widely used in the food, pharmaceutical, cosmetic and health industries today (Omid Beigi, 2013). Managing the use of fertilizers, including chemical fertilizers, affects the performance of medicinal plants. Proper nutrition and absorption of essential elements and improving their concentration in the seed play a significant role in increasing the quantitative and qualitative performance of the medicinal plant fennel (Kapoor et al., 2004). The present study was designed and implemented with the aim of evaluating the effect of different chemical, organic, and biological nutritional systems on the yield and nutrient absorption of fennel.
 
Materials and Methods
The experiment was conducted in a split-plot randomized complete block design with three replications during the 2023-2024 crop year at the research farm of Khuzestan University of Agricultural Sciences and Natural Resources, Khuzestan, Iran. In the main plots, the levels of Urea nitrogen fertilizer and sugarcane residue compost were: A₁: control, A₂: 150 kg.ha^-1 nitrogen, A₃: 112.5 kg.ha^-1 nitrogen + 8 t.ha^-1 sugarcane compost, A₄: 75 kg.ha^-1 nitrogen + 16 t.ha^-1 sugarcane compost, A₅: 37.5 kg.ha^-1 nitrogen + 24 t.ha^-1 sugarcane compost, and A₆: 32 tons/ha sugarcane compost. In the subplots, the seed inoculation treatment with Biofarm biofertilizer was investigated, including B₀: control and B₁: treatment. The studied traits included grain yield, biological yield, essential oil percentage and yield, nitrogen percentage and absorption, nitrogen efficiency indices, phosphorus, potassium, iron, and zinc percentage.
 
 
Results and Discussion
The highest seed yield was obtained in the A₄B₀ and A₂B₁ treatment levels (998 and 938 kg.ha^-1). The highest percentage of essential oil was obtained in the A₂ treatment level (2.26%) and the highest yield of fennel essential oil was obtained in the A₂B₁ treatment level (13.22 kg.ha^-1). The highest percentage and absorption of nitrogen were obtained in the A₂ treatment level (2.35%) and (68.01 kg.ha^-1), respectively. The highest agronomic efficiency of nitrogen was obtained in the A₄B₀ treatment level (6.85 kg.kg^-1). The highest phosphorus and potassium content of the whole plant was obtained in the A₅ treatment level (50.8 and 193.75 mg.kg^-1), respectively, and the highest iron and zinc concentration of the whole plant was obtained in the A₆ treatment level (3.01 and 0.56 mg.kg^-1) of dry matter.
 
Conclusion
In the present experiment, the highest grain yield was obtained with the application of 75 kg.ha^-1of nitrogen and 16 tons.ha^-1of sugarcane compost, which had no significant difference with the application of 150 kg.ha^-1of nitrogen. Also, the highest biological and essential oil yield was obtained with the application of 150 kg.ha^-1of nitrogen and with the application of biofertilizer. In fact, the application of chemical nitrogen fertilizer in combination with organic fertilizer of sugarcane compost and the application of biofertilizer increased grain yield and essential oil and increased the absorption of low- and high-consumption elements required by the fennel plant. It also had similar effects in increasing yield compared to the application of chemical fertilizers, which can replace combined fertilizers with chemical fertilizers.