Effect of organic manures and biostimulants on productivity and quality of medicinal herbs

Abstract:

Organic herb production has expanded across West Africa, yet systematic data on how different organic nutrient sources and biostimulants affect both yield and phytochemical quality remain scarce. This research compared the effects of four organic manures (farmyard manure, vermicompost, neem cake, and poultry litter) combined with foliar application of seaweed extract at three concentrations (0%, 1.0%, and 2.0%) on the growth, yield, and essential oil content of holy basil (Ocimum tenuiflorum) and spearmint (Mentha spicata). A factorial randomised complete block design with three replications was laid out at the organic research farm of Ogun Valley Agricultural College, Abeokuta, Nigeria, from June to November 2022. Vermicompost combined with 1.0% seaweed extract produced the highest fresh herb yield for both species 2.13 t/ha for basil and 1.98 t/ha for mint and the highest essential oil content (1.87% and 1.62%, respectively). Poultry litter alone gave the lowest quality scores despite acceptable yields. The results point to vermicompost as the most effective organic nutrient source and suggest that moderate seaweed extract application can boost both productivity and phytochemical quality in tropical medicinal herb systems.