Effects of calcium foliar fertilization on growth, physiology and productivity of fennel (Foeniculum vulgare Mill.)

Fennel ( Foeniculum vulgare Mill.), a traditional aromatic crop, is widely cultivated for its seeds and EO content. Calcium (Ca), a crucial macronutrient, enhances plant structural integrity, stress tolerance, and secondary metabolism, yet limited information is available on its role in fennel productivity. The present study investigates the effects of foliar-applied Ca on the growth, physiological responses, yield, and essential oil (EO) content of fennel under semi-arid field conditions. Six calcium chloride (CaCl 2 ) treatments (0, 16, 32, 64, 128, and 256 mg L⁻ 1 Ca) were tested on the crop in a randomized complete block design. All above parameters were recorded and analyzed using ANOVA followed by DMRT. Results showed that foliar application of Ca significantly improved the overall performance of fennel, with 64 mg L −1 Ca as the optimal concentration. This dose significantly increased plant height by 13.7%, number of branches by 61.7%, stem diameter by 40.8%, and fresh and dry biomass by 50.9% and 56.6%, respectively, over their respective control. Physiological traits also improved, including total chlorophyll (34.9%), carotenoids (41.6%), NDVI (27.5%), and total soluble solids (46.2%). In addition, different yield parameters increased by the optimum dose compared with the control. The findings highlight foliar Ca fertilization as a simple, effective, and sustainable agronomic strategy for enhancing fennel growth and productivity.