Determination of growth, leaf yield, quality and safety of potted Ocimum gratissimum L. cultivated using different fertilizer types

Purpose: The purpose of the study was to produce compost and compare the effect with other fertilizer types on scent leaf vegetative growth, yield, nutrient contents and heavy metal accumulation for safety of consumers. Method: Cow dung, compost, NPK fertilizer and urea were applied to scent leaf stem cuttings at 2 weeks after planting. Control was zero application of fertilizer. Treatments were replicated four times in a completely randomized design. Concentrations of Cu, Fe, Pb, Cd, Zn and Ni in the leaves were determined at 8 weeks after treatment application (WATA). Results: Compost increased plant height from 32.40 to 66.25 cm while zero application of fertilizer increased plant height from 20.75 to 38.25 cm between 2 to 8 WATA. Compost (3.88 tha-1) significantly (p<0.05) produced highest leaf yield than zero application of fertilizer (1.29 tha-1). Fe, Cu, Pb accumulation were lowest in scent leaf produced with NPK fertilizer while Zn, Ni and Cd accumulation were lowest in scent leaf produced with cow dung. Pb was higher in scent leaf produced with compost (0.48 ± 0.09 mg kg-1) and lower in scent leaf cultivated with NPk fertilizer (0.11 ± 0.06 mg kg-1). Despite the high content of heavy metals in scent leaf produced with compost, heavy metal bioaccumulations were below FAO/WHO permissible values. Conclusion: Soils amendment with 5 tha-1 of compost showed superiority over other fertilizer types in terms of growth and leaf yield of scent leaf. Cow dung and NPK fertilizer suppressed bioaccumulation of heavy metals in scent leaf and promoted nutrient quality and safety of the scent leaf. Research Highlights • Organic and inorganic fertilizers can be used to amend the soil • Organic and inorganic fertilizers contain heavy metals • Crops absorb heavy metals and heavy metals above FAO/WHO permissible value makes the crop unsafe • Compost showed superiority in improving growth and yield of scent leaf above other fertilizers • Concentration of heavy metals in scent leaf grown with compost was below FAO/WHO permissible value