Aquaponics is a food production technology that combines aquaculture and hydroponics in an integrated recirculating system without soil (Rakocy et al., 2006). The aquaponics ecosystem is composed by fish, bacteria, and plants (Somerville et al., 2014). Fish are fed with dry feed; fish waste is generated by direct excretion into the fish tanks, and organic waste metabolites are converted by microbial breakdown in the recirculating system filters—where ammonia is converted to nitrate by nitrifying bacteria (Love et al., 2014); and nutrients are absorbed by the plants cultivated hydroponically (Rakocy et al., 2011). Solid fish waste eliminated after food digestion provides most of the nutrients required for plant nutrition, except calcium and iron, which are commonly supplemented. The aquaculture effluent flows through deep-flow culture hydroponic troughs, and a closed system recirculates the water back to the fish-rearing tanks for reuse (Rakocy et al., 2011).
The integration of fish and vegetable production in the UVI Commercial Aquaponics System uses a small land area, conserves water, limits waste discharged into the environment (Boxman et al., 2017), and recovers nutrients from fish production into valuable vegetable crops. A standard protocol has been developed for the production of Nile tilapia (Oreochromis niloticus), which yields up to 11,000 lb per annum (Rakocy et al., 2006). The production of many vegetable crops also has been studied, but because of specific growth patterns and differences of marketable product, no single protocol is promoted.
In general, leafy vegetables grow well with the abundant nitrogen in the system, have a short production period, and are in high demand. Lettuce (Lactuca sativa) has been produced continuously in the UVI Commercial Aquaponics System, including a diversity of cultivars and cultural practices (Rakocy et al., 1997). Economic studies of lettuce and basil production also have been conducted (Bailey et al., 1997; Rakocy et al., 2004a). Each crop yields different revenue per unit area, and this variation must be considered when selecting cultivars to produce and obtain the highest returns for the farmer (Bailey and Ferrarezi, 2017).
Basil is a fast-growing crop commonly cultivated in aquaponics systems by commercial producers, hobbyists, and educators (Love et al., 2014). The crop’s distinctive aroma and flavor derive from essential oils, plant phenolics, flavonoids, and phenylpropanoids (Juliani and Simon, 2002). The genus Ocimum comprises more than 30 species, and is divided into basil types, which include sweet (Ocimum basilicum), lemon (Ocimum citriodorum), dwarf bush (Ocimum minimum), purple (O. basilicum var. purpurescens), and thai (O. basilicum var. thyrsiflorum). Basil cultivars can be produced for different target markets such as essential oils, pharmaceuticals, ornamental plants, or as a culinary herb for fresh or dry spices (Kaurinovic et al., 2011; Walters and Currey, 2015). Purple basils contain higher anthocyanin levels (Simon et al., 1999) and are grown for culinary purposes and teas, especially as a potential source of anthocyanins because of antioxidant properties (Juliani and Simon, 2002). Basil can be produced in aquaponics using one planting date (batch) or staggered planting dates, resulting in the production of 7.8 and 7.2 kg·m−2 of shoot fresh weight, respectively, with a density of 8 plants/m2 (Rakocy et al., 2004b).
Choosing high-value crops is one of the strategies to maximize income in aquaponics systems (Dediu et al., 2012), increasing grower portfolio and minimizing the production risks. Previous research has indicated that basil is a high-value crop for aquaponics (Rakocy et al., 2004b). However, little research has been conducted to produce different basil types and cultivars in commercial-scale aquaponics (Love et al., 2015). Walters and Currey (2015) recently compared hydroponics systems and basil cultivars in greenhouse conditions with environmental control. Saha et al. (2016) cultivated basil under soilless agricultural systems (aquaponics vs. hydroponics), without indicating how different cultivars perform. The evaluation of plant adaptation in tropical conditions is essential to recommend new cultivars for the UVI Commercial Aquaponics System. Yield per area is a primary concern so that cultivars with the greatest biomass can be selected to maximize the production per area. Plant height, width, leaf area, number of leaves, and other aspects of plant morphology are also useful to evaluate crop performance. Our objective was to identify suitable basil cultivars for tropical outdoor aquaponics production using the UVI Commercial Aquaponics System to support farmers picking adapted cultivars.
Bailey, D.S. & Ferrarezi, R.S. 2017 Valuation of vegetable crops produced in the UVI commercial aquaponics system Aquacult. Rpt. 7 77 82
Bailey, D.S., Rakocy, J.E., Cole, W.M. & Shultz, K.A. 1997 Economic analysis of a commercial-scale aquaponic system for the production of tilapia and lettuce, p. 603–612. In: K. Fitzsimmons (ed.). Tilapia aquaculture. Proc. Fourth Intl. Symp. Tilapia Aquacult., Orlando, FL
Boxman, S.E., Zhang, Q., Bailey, D.S. & Trotz, M.A. 2017 Life cycle assessment of a commercial-scale freshwater aquaponic system Environ. Eng. Sci. 34 299 311
Dediu, L., Cristea, V. & Xiaoshuan, Z. 2012 Waste production and valorization in an integrated aquaponic system with bester and lettuce Afr. J. Biotechnol. 11 2349 2358
Juliani, H.R. & Simon, J.E. 2002 Antioxidant activity of basil, p. 575–579. In: J. Janick and A. Whipkey (eds.). Trends in new crops and new uses. ASHS Press, Alexandria, VA
Kamal, A.H.M.M. & Mair, G.C. 2005 Salinity tolerance in superior genotypes of tilapia, Oreochromis niloticus, Oreochromis mossambicus and their hybrids Aquaculture 247 189 201
Kaurinovic, B., Popovic, M., Vlaisavljevic, S. & Trivic, S. 2011 Antioxidant capacity of Ocimum basilicum L. and Origanum vulgare L. extracts Molecules 16 7401 7414
Kottek, M., Grieser, J., Beck, C., Rudolf, B. & Rubel, F. 2006 World map of the Köppen-Geiger climate classification updated Meteorologische Zeitschrift 15 259 263
Love, D.C., Fry, J.P., Genello, L., Hill, E.S., Frederick, J.A., Li, X. & Semmens, K. 2014 An international survey of aquaponics practitioners PLoS One 9 e102662
Love, D.C., Fry, J.P., Li, X., Hill, E.S., Genello, L., Semmens, K. & Thompson, R.E. 2015 Commercial aquaponics production and profitability: Findings from an international survey Aquaculture 435 67 74
Rakocy, J.E., Bailey, D.S., Shultz, K.A. & Cole, W.M. 1997 Evaluation of a commercial-scale aquaponic unit for the production of tilapia and lettuce, p. 357–372. In: K. Fitzsimmons (ed.). Tilapia Aquaculture. Proc. Fourth Intl. Symp. Tilapia Aquacult., Orlando, FL
Rakocy, J.E., Bailey, D.S., Shultz, R.C. & Danaher, J.J. 2011 A commercial-scale aquaponic system developed at the University of the Virgin Islands, p. 336–343. In: L. Liping and K. Fitzsimmons (eds.). Better science, better fish, better life. Proc. Ninth Intl. Symp. Tilapia Aquacult., Shanghai, China
Rakocy, J.E., Bailey, D.S., Shultz, R.C. & Thoman, E.S. 2004a Update on tilapia and vegetable production in the UVI aquaponic system, p. 676–690. In: R. Bolivar, G. Mair, and K. Fitzsimmons (eds.). New dimensions in farmed tilapia. Proc. Sixth Intl. Symp. Tilapia Aquacult., Manila, Philippines
Rakocy, J.E., Masser, M.P. & Losordo, T.M. 2006 Recirculating aquaculture tank production systems: Aquaponics—Integrating fish and plant culture Southern Reg. Aquaculture Ctr. Publ. 454 1 16
Rakocy, J.E., Shultz, R.C., Bailey, D.S. & Thoman, E.S. 2004b Aquaponic production of tilapia and basil: Comparing a batch and staggered cropping system Acta Hort. 648 63 69
Saha, S., Monroe, A. & Day, M.R. 2016 Growth, yield, plant quality and nutrition of basil (Ocimum basilicum L.) under soilless agricultural systems Ann. Agr. Sci. 61 181 186
Simon, J.E., Morales, M.R., Phippen, W.B., Vieira, R.F. & Hao, Z. 1999 Basil: A source of aroma compounds and a popular culinary and ornamental herb, p. 499–505. In: J. Janick (ed.). Perspectives on new crops and new uses. ASHS Press, Alexandria, VA
Somerville, C., Cohen, M., Pantanella, E., Stankus, A. & Lovatelli, A. 2014 Small-scale aquaponic food production: Integrated fish and plant farming. FAO Fisheries Aquaculture Tech. Paper No. 589
Timmons, M.B. & Ebeling, J.M. 2002 Recirculating aquaculture. 2nd ed. Northeastern Regional Aquacult. Pub. No. 01-002
Walters, K.J. 2015 Quantifying the effects of hydroponic systems, nutrient solution, and air temperature on growth and development of basil (Ocimum L.) species. Iowa State Univ., Ames, MS Thesis