Two field experiment was conducted on fennel (Feoniculum vulgare, Mill.) during the two successive seasons of 2018/2019 and 2019/2020 in the Experimental Farm of EL-Quassasin Horticultural Research Station, Ismailia Governorate, Egypt. This investigation aimed to study the impacts of spraying fennel
plants with glutamine, tyrosine and glutamine+ tyrosine at the rate of 100 ppm beside the control treatment (0.0 ppm) under four levels of potassium fertilization rates as 0.0, 24, 48 and 72 kg K2O/feddan, on growth, yield
components, volatile oil production and some constituents. The results ensured that fertilizing fennel plants with 72 kg K2O per feddan, regardless amino acid treatments, significantly increased vegetative growth (plant height,
branch number and total fresh and dry weights of herb per plant), yield components (number of umbels per plant, fruit yield per plant and per feddan), volatile oil production (volatile oil percentage, volatile oil yield per plant and
per feddan) as well as total chlorophyll content (a+b) in leaves, total carbohydrates and potassium percentage in fruits compared to control and the other rates under study. Moreover, applying fennel plants with glutamine +
tyrosine at 100 ppm of each, regardless potassium rates treatments, which followed by glutamine at 100 ppm alone significantly improved abovementioned parameters compared to control (sprayed with tap water). Concerning the
interaction between fertilization with potassium and amino acids treatments, generally, the combination treatment between the highest rate of potassium fertilization and spraying plants with 100 ppm glutamine + tyrosine is the
best treatment for growth, yield components, volatile oil production and pigments of fennel plants under Ismailia Governorate conditions.