Scientia Horticulturae 159 (2013) 113–121 Contents lists available at SciVerse ScienceDirect Scientia Horticulturae journal homepage: www.elsevier.com/locate/scihorti Growing carrots hydroponically using perlite substrates Md. Asaduzzaman a,b,c , Yutaro Kobayashi a , Md. Fuad Mondal a , Takuya Ban d , Hitoshi Matsubara e , Fumihiko Adachi a , Toshiki Asao a,∗ a Department of Agriculture, Faculty of Life and Environmental Science, Shimane University, 2059 Kamihonjo, Matsue, Shimane 690-1102, Japan b United Graduate School of Agricultural Sciences, Tottori University, Koyama-cho, Minami Tottori, Tottori 680-8553, Japan c Bangladesh Agricultural Research Institute, Gazipur 1701, Bangladesh d Faculty of Agriculture, Tokyo University of Agriculture and Technology, Fuchu, Tokyo 183-8509, Japan e Suntory Holdings Limited, Suntory Research Center, Mishima-gun, Osaka 618-8503, Japan article info Article history: Received 17 January 2013 Received in revised form 3 April 2013 Accepted 30 April 2013 Keywords: Daucus carota L. Soilless culture Nutrient solution concentration Residual nutrient abstract Perlite substrate and nutrient solution were studied for growing carrot [Daucus carota L. cv. Dr. Carotene 5] hydroponically. Three independent studies were conducted to determine the size of perlite particle and concentrations of nutrient solution for growing carrot in hydroponics by evaluating their effects on growth, root yield and qualities of carrot. In the first study, carrots were grown in 1.2 or 5.0 mm with 12.5, 25, 50 and 75% ‘Enshi’ nutrient solution. Plants grown in 1.2 mm perlites with 50 and 75% nutrient solution produced about 15 and 28% higher root yield, respectively than those plants grown in 5.0 mm with same concentration, which was attributed by its longer roots. In the second study, carrots were grown in 0.6, 1.2, 2.5, and 5.0 mm perlites and with 25, 50, 100, 200, and 300% of nutrient solution. It was found that, carrot plants grown in 0.6 mm perlite supplied with 100% nutrient solution produced significantly higher root yield compared to larger perlite particles and higher concentrations of nutrient solution. In the third study, once used perlites of 0.3, 0.6, and 1.2 mm particle and 50, 75, 100, and 150% nutrient solution were investigated and greater root yield was obtained from carrots grown in 0.6 mm than in 0.3 or 1.2 mm perlite with 75% nutrient solution. Carrots grown in 0.3 mm perlites produced shorter roots, wider near the proximal end and whitish in the distal end due to excessive water content causing oxygen deficiency. Carrot root length was greatly hampered leading to decreased root yield in plants grown in 0.3 mm perlites compared to other perlite sizes at all concentrations except 100%. This ultra fine perlite hold excessive water causing oxygen deficiency in the substrate air zone and as a result roots become whitish with reduced amount of carotenoids content. Reused perlite culture in the third study lead to maximum root yield at 75% nutrient solution whereas it was with 100% in the second study, which was possibly due to residual nutrient available in the reused perlite which in turn lowers the demand of nutrients in the second culture. Year and growing season along with reused perlite has results in lower root yield and quality in the last two cultures in autumn 2009 and 2010. Therefore, we recommended 0.6 mm perlite and 100% (for first culture) or 75% (for second culture) ‘Enshi’ nutrient solution for growing carrots hydroponically with maximum yield and higher quality. © 2013 Elsevier B.V. All rights reserved. 1. Introduction The carrots [Daucus carota L.], rich in carotenoids, is among the top-ten most economically important vegetable crops in the world, in terms of both area of production and market value (FAOSTAT, 2012; Fontes and Vilela, 2003). It has been widely used as a material for juice production both alone and mixed with other vegetables and fruits with high quality of taste, sweet- ness and flavor. Regular intake of carrot juice can help us to stay away from different degenerative diseases like cataracts, glaucoma, ∗ Corresponding author. Tel.: +81 852 34 1817; fax: +81 852 34 1823. E-mail addresses: asadcbt@yahoo.com (Md. Asaduzzaman), asao@life.shimane-u.ac.jp (T. Asao). cardiovascular complications, and even cancer as it has high antiox- idant properties. In this regard, hydroponically grown carrots provide outstanding quality, flavor and nutrition (Gichuhi et al., 2009). It allows clean cultivation of roots as the most of pests are soil born which is no longer a concern in hydroponics. Compared to traditional systems, hydroponic carrots are grown with a bigger assurance of nutritional content. Since a regular nutritional test- ing is conducted in the hydroponic growing system, so it can be more easy defined whether the desired amount of nutritional con- tent is present in the carrots or not. In addition, undesired nutrient contents, for instance nitrites, heavy metal contamination can be easily kept away from the system. Therefore, hydroponics system has been evaluated for growing potatoes, sweet potatoes, sugar beets and peanuts for controlled ecological life support system (Hill et al., 1992). 0304-4238/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.scienta.2013.04.038