Today, fresh herbs can be sourced as live container-grown plants year-round in the produce section of most retailers. Commercial fertilizers are selected based on several factors, including the ratio of ammonium- and nitrate-nitrogen and phosphorous concentration. The objective of this research was to quantify the effects of increasing phosphorus concentrations alongside different ratios of nitrate and ammoniacal nitrogen concentrations in commercial water-soluble fertilizers on the post-production performance of containerized culinary herbs. Seedlings of sweet basil (Ocimum basilicum ‘Genovese’) were transplanted into 11.4 cm-diameter containers filled with soilless substrate compromised of peat moss and coarse perlite. Upon transplant and throughout the experiment, seedlings were irrigated with commercially available water-soluble fertilizer (WSF) solutions variying in potential acidity (PA) or potential basicity (PB) and the ratio of nitrogen to phosphorous (N:P), including: 15N-0.9P-12.5K (PB 195 CCE/ton; 167N:10P); 15N-1.8P-16.6K (PB 77 CCE/ton; 83N:10P); 15N-2.2P-12.5K (PB 69 CCE/ton; 68N:10P); 15N-4.8P-14.1K (PA 58 CCE/ton; 15N-7P-24.1K (PA 122 CCE/ton; 21N:10P); and 20N-4.4P-16.6K (PA 401 CCE/ton; 45N:10P); 31N:10P). Plants were grown in two different phases: 1) in a greenhouse for 28 d at 22°/18° and 12 mol∙m–2∙d–1 to simulate a greenhouse production phase; and 2) in a growth chamber for 7 d at 20° ADT and 1 mol∙m–2∙d–1, to simulate a production and retail environment, respectively. After each phase, data was collected on half of the plants.. Plant height increased by 1.7 cm across treatments between the end of the greenhouse phase and the end retail phase. The relative growth rate of fresh mass accumulation decreased from 5.7 g∙d–1 during production to 1.2 g∙d–1 during the retail phase. Similarly, relative growth rate of dry mass accumulation decreased from 0.5 g∙d–1 during production to -0.2 g∙d–1 during the retail phase. The pH during the greenhouse phase was higher for basil fertilized with higher-nitrate formulations compared to those receiving fertilizers with more ammonium, but these differences were diminished during the retail phase. The results of this study indicate environment has a greater impact on plant growth and development than both the potential basicity or acidity and phosphorus content of fertilizer provided.
