Controlled-release and Water-soluble Fertilizers Affect Growth and Tissue Nutrient Concentrations of Basil, Dill, and Parsley

Limited information is available for fertilizing containerized herbs to produce appropriately sized plants with adequate tissue nutrient concentrations. The objectives of this research were to quantify growth and tissue mineral nutrient concentrations of containerized culinary herbs fertilized with water-soluble (WSF) or controlled-release fertilizer during production. Seedlings of ‘Italian Large Leaf’ basil (Ocimum basilicum L.), ‘Fernleaf’ dill (Anethum graveloens L.), and ‘Giant Parsley of Italy’ parsley (Petroselinum crispum Mill.) were transplanted into 10.4-cm-diameter containers filled with soilless substrate comprised of (by vol.) 75% sphagnum peat moss and 25% perlite containing 0, 1, 2.5, 5, or 10 lbs∙yd^–3 CRF fertilizer (16–2.2–9.1). Beginning immediately at transplant, plants with no CRF were provided with 0 (control), 50, 100, 200, or 400 mg∙L^–1 N from a complete, WSF fertilizer (21–2.2–16.6); plants with CRF were irrigated with clear water. Data collected included height, widest width, and perpendicular width. Growth Index (GI) was calculated. Plants were harvested at the substrate surface, plants were weighed, fresh mass was recorded, then shoots were triple-rinsed in deionized water. Shoots were then dried and shoot dry mass (SDM) was recorded. Dried shoots were submitted to a commercial laboratory for nutrient analyses. Within each species, untreated control plants had smaller GI, SDM, and lower tissue N levels than plants at all other fertilizer levels and sources. Differences in GI across non-control treatments occurred for basil and parsley, though fewer differences were observed for parsley. For example, basil supplied with 200 mg∙L^–1 N WSF were 33% larger than plants supplied with 50 mg∙L^–1 N. Conversely, parsley supplied with 200 mg∙L^–1 N were similar to plants grown with 50 mg∙L^–1 N, while no differences in GI were observed among fertilized dill plants. Fresh mass of dill treated with 10 lbs∙yd^–3 CRF (14.0 g) was similar to 50 and 100 mg∙L^–1 N (13.7 and 13.7 g, respectively). Alternatively, basil supplied with 10 lbs∙yd^–3 CRF were 32% and 19% larger than plants treated with 50 and 100 mg∙L^–1 N, respectively. Tissue N, P, and K concentrations were within or above recommended ranges for all species supplied with 5 and 10 lbs∙yd^–3 CRF and 200 and 400 mg∙L^–1 N, though there were no visible symptoms of nutrient deficiencies for plants provided with less fertilizer. Producers should use this information to select appropriate fertilizer concentrations for containerized basil, dill, and parsley production.