Efficient utilization of aquaculture effluents to maximize plant growth, yield, and essential oils composition of Origanum majorana cultivation

Aquaculture effluents are nutrient-rich water containing both inorganic and organic nutrients with a potential to replace chemical fertilizer applications under integrated agricultural systems. A field experiment was conducted to determine the effect of fish effluent as an irrigation water source on the growth, yield, and essential oil composition of sweet marjoram. A randomized complete block design was followed with three irrigation treatments and three replicates i.e. fertigation with chemical fertilizers (control), irrigation with effluents only (effluents), and mixed treatment with 50% effluent and 50% chemical fertilizers (mixed). Marjoram seedlings were transplanted, and two cuts were done at the flowering stage. Samples were analyzed for yield and essential oil. In the first cut, effluents recorded an average of 40.4 cm height and 30.2 branches. It also had significantly higher yields, reaching 12.5ton ha⁻¹ and 2.8ton ha⁻¹ for fresh and dry yields, respectively. For the second cut, mixed had the highest average number of branches (58.8) and average height (59.2 cm). It recorded the highest yields of 26.5ton ha⁻¹ and 10.5ton ha⁻¹ of fresh and dry yields, respectively. Similarly, mixed gave the highest oil content (0.98%), compared to the control (0.84%). Essential oil analysis showed six main constituents; terpinen-4-ol (27.11–32.38%), β-terpineol (9.84–17.22%), γ-terpinene (11.09–15.55%), α-terpinene (6.68–10.34%), sabinene (8.18–9.25%), and cis-sabinene hydrate (5.01–8.64%). The results, therefore, suggest that growing marjoram with a mixed treatment would give the best herbage yields and the highest essential oils with reduced environmental impacts.