Effects of organic fertilisers on growth, yield and nutritional content of sweet basil (Ocimum basilicum L.)

Sweet basil (Ocimum basilicum L.) is one of the major essential oil-producing species used in culinary and fragrance applications. However, there is a dearth of information pertaining to its organic production in the country. A field study laid out in a Randomized Complete Block Design (RCBD) was conducted at the Horticulture Farm, Luyengo Campus, University of Eswatini to assess the effects of organic fertilisers on the growth, yield and nutritional content of basil. This study consisted of four treatments replicated four times. The organic fertilisers used were chicken manure, kraal (cattle) manure and compost. The rates of application were 40 t/ha for the manures. Chemical fertilizer 2:3:2 (22) + 0.5 Zinc (Zn) and limestone ammonium nitrate (LAN 28%) were included at application rates of 150 kg/ha basal dressing and 100 kg/ha LAN top dressing, respectively. The results showed that the type of organic fertilizer applied affected the growth and yield of sweet basil. A trend in the superiority of the different types of organic fertilisers was observed as chicken manure exhibited higher values of the number of leaves (134.2), branches (78.6), leaf area (30.2 cm2)) and chlorophyll content (68.2 CCI), fresh leaf mass (355 g), and fresh mass of basil plant (691 g). Kraal manure was the second, followed by chemical fertilizer and lastly compost. There were no significant (P > 0.05) differences in P, K, Mn, Cu, and Zn content due to the application of different organic fertilisers. Calcium, Mg and Fe showed significant (p < 0.05) differences among the treatments. The use of chicken manure in the production of basil should be encouraged because its application resulted in relatively higher growth and yields compared to the other fertilisers. Keywords: Organic fertilizers, growth, basil, medicinal properties, mineral content.