Effect of Water Recirculation Duration and Shading on Lettuce (Lactuca sativa) Growth and Leaf Nitrate Content in a Commercial Aquaponic System

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1 Turkish Journl of Fisheries nd Aqutic Sciences 16: (2016) ISSN DOI: / v16_2_11 RESEARCH PAPER Effect of Wter Recircultion Durtion nd Shding on Lettuce (Lctuc stiv) Growth nd Lef Nitrte Content in Commercil Aquponic System Pkms Sreejriy 1,*, Thoms Rynud 2, Lionel Dbbdie 3, Amrrtne Ykupitiyge 1 1 Asin Institute of Technology (AIT), School of Environment, Resources nd Development (SERD), Aquculture nd Aqutic Resources Mngement (AARM), Pthumthni, Thilnd. 2 Assocition Réunionnise pour le Développement de l'aquculture (ARDA) quculture reserch center, L ÉtngSléles BinsL Réunion, Frnce. 3 Centre de Coopértion Interntionle en Recherche Agronomique pour le Développement (CIRAD), UMR ISEM, F34398 Montpellier, Frnce. * Corresponding Author: Tel.: ; Emil: pkms_grte@hotmil.com Abstrct Received 03 Mrch 2016 Accepted 27 Mrch 2016 Two experiments were conducted to evlute the effects of three wter recirculting durtion (dytime (07.00h to18.00h); nighttime (18.00h to 07.00h); nd 24 hours control) nd shding (30%, 60% nd no shding control), respectively, on growth nd sp s nitrte content of lettuce in commercil quponic system integrted with red tilpi culture. First experiment showed tht wter recirculting time did not ffect the lettuce growth, thus offering the possibility to increse quponics profitbility by reducing the opertionl cost. The second experiment reveled tht shding ffected nitrte content in the sp of the lef midribs, but it remined in rnge specified by EU regultions in ll tretments. The highest lettuce growth ws observed t the rte of 30% shding wheres 60% shding gve the lowest growth (P<0.05). Keywords: Recircultion durtion, quponic system, lettuce, nitrte, shding. Introduction Unlike hydroponics, which entirely relies on nutrient supplements, quponics integrtes recirculting quculture system (RAS) with hydroponics by using nitrogenrich fish wstes s n orgnic fertilizer (Pntnell et l., 2010; Blidriu nd Groze, 2011; Love et l., 2015). Although commercil quponic systems exist, high investment nd opertion costs of RAS cn be significnt constrint for the doption of this system in developing countries (Rkocy nd Biley, 2003; Mrtins et l., 2010). A higher profitbility nd reduction of opertionl costs re needed to mke quponics n economiclly vible food production system (Klinger nd Nylor, 2012; God et l., 2015). Reduction in wter recircultion period might be solution for reducing opertionl costs. However, limited reserch hs been conducted to determine how wter recircultion time ffects plnt growth performnce, wter qulity, nutrient removl nd the qulity nd food sfety (Cometti et l., 2011; Liu nd Yng, 2012). Previous studies hve shown tht nitrte content in cultivted plnts is prtly determined by culture prctices nd in some conditions it could rech concentrtions deemed hzrdous for humn consumption. This hs become globl concern; for exmple, the Europen Union (EU) limits the mximum permissible lef nitrte concentrtions in vegetbles to 4,500 mg kg 1 NO 3 fresh weight (FW) for the winter seson crops nd 2500 mg kg 1 NO 3 fresh weight (FW) for the summer crops (Commission Regultion (EC) No 1881/2006, 2006; Cometti et l., 2011; Liu nd Yng, 2012). Environmentl fctors, such s excessive light intensity, hve been identified s one of the mjor fctors ffecting NO 3 uptke in vegetbles (Ling nd Chien, 2013) but limiting light intensity ffects the plnt growth (Sntmri, 2006) nd nutrient uptke. This pper presents the results of two experiments conducted to evlute different wter recircultion durtions nd shdings on lettuce growth nd nitrte content in the sp. This study lso evluted whether the different culture prctices employed in this study mintin the nitrte content of the sp in complince with food sfety regultions. Mterils nd Methods Aquponic System t Assocition Réunionnise pour le Développement De l'aquculture (ARDA) The experiments were conducted in pilot commercilscle quponics system locted in the experimentl reserch sttion of the Assocition Published by Centrl Fisheries Reserch Institute (CFRI) Trbzon, Turkey in coopertion with Jpn Interntionl Coopertion Agency (JICA), Jpn

2 312 P. Sreejriy et l. / Turk. J. Fish. Aqut. Sci. 16: (2016) Réunionnise pour le Développement de l'aquculture (ARDA), in ÉtngSlélesBins, Reunion islnd (S 21 17' 7.21", E 55 22' 41.80"). The quponic system ws comprised of three components: (1) fish rering system with four fish tnks; (2) filtrtion system with mechnicl nd biologicl filter; nd (3) hydroponic system with six hydroponic tnks (Figure 1). Four 5 m 3 tnks were stocked with hybrid tilpi (Oreochromis niloticus, O. mossmbicus X O. hornorum X O. ureus; Broiller nd D'Cott, 2001) t density of 1000, 1000, 500, nd 500 fish per tnk, respectively. The initil fish weights in the 4 tnks were 52g, 145g, 168g nd 218g, respectively. Initil biomss in ll tnks ws pproximtely 500 kg. Fish were fed dily with commercil pelleted feed contining 34% protein (Nutrim GED 4.5, Reunion, Frnce) using n utomtic feeder from 08:00h to 16:00h. Fish tnk effluents were llowed to flow by grvity to the filter system, mde of two solids removl tnks, eight filtrtion tnks contining discrded net cges, nd one biofilter tnk contining biobll (Polymeric, Chin). Treted wter ws pumped to the hydroponic tnks t rte of 2 m 3 h 1. Wter level in ech tnk ws kept t 0.3 m in depth mintining volume of 6 m 3. Six 3 m 2 Styrofom floting rfts, ech contining 50 lettuce seedlings (16 lettuces m 2 ) were plced in the hydroponics tnks to cover the whole wter surfce (except t the inlets nd outlets res, where wter smples were collected). Ech hydroponic tnk hd 300 lettuces seedlings. Lettuce plnts were pproximtely 25 cm prt. The seedlings from loclly vilble vriety of lettuce (Lctuc stiv) were purchsed from privte hydroponic frm in Reunion Islnd. The plnts were three weeks old (fourlef stge) t the beginning of the experiments. The outflow of hydroponics system ws drined to sump tnk vi dringe cnl nd then pumped bck to the fish tnks. For the biofilter to perform well, the system ws lredy in opertion 30 dys before strting the experiment, s recommended, to enhnce bcteril growth (FAO, 2014). Experimentl Design Both experiments hd three tretments including the control. Ech tretment ws duplicted using completely rndom design. In Experiment 1, three wter recircultion durtion were tested for 28 dys conducted between September to October, 2012), i.e. (i) (T1), dytime wter recircultion durtion (11 hours from 07:00h to 18:00h); (ii) (T2), nighttime wter recircultion durtion (13 hours from 18:00h to 07:00h); nd (iii) (T3), the control (24 hours wter recircultion durtion). In Experiment 2, which ws conducted in 2012, three shding rtes were tested for 21 dys, i.e (i) (S1), 60% shding (ii) (S2), 30% shding; nd (iii) (S3) control (no shding). Loclly vilble green griculturl shde nets of 30% nd 60% density were used for shding. Wter Qulity Smpling nd Anlysis In Experiment 1 nd 2, wter smples were collected in the hydroponic tnk s inlets (treted fish tnk effluent) nd outlets (inside the tnk of lettuce t the vicinity of the wter outlets). Wter temperture, dissolved oxygen (DO Meter ID100P, Jpn), conductivity (Conductivity meter I1200, USA), ph (HI 9025, Hnn Instruments, USA) nd NO 3 concentrtion were mesured dily t 07:00h nd 18:00h. Ammoni nitrogen (NH 3 ) ws determined by using phente method, nitrite (NO 2 ) by using colorimetric method, nitrte (NO 3 ) by using cdmium reduction method, nd orthophosphte (PO 4 3 ) by using scorbic cid method (APHA, 1998). The wter smples were collected weekly t 08:00h from the inlets nd outlets. In ddition, in experiment 1, NO 3 ws mesured dily t 07:00h nd18:00h, nd weekly t 08:00h. Lettuce Growth Mesurement Lettuce height nd dimeter were mesured weekly using ruler, nd the weight ws recorded using digitl scles. The weight, height nd dimeter of lettuce in both experiments were mesured by rndomly smpling 30 plnts from ech replicte t the end of ech experiment. Dt Anlysis Wter qulity nd growth prmeters were clculted using the following equtions: Nitrte removl (mg L 1 ) = NO 3 concentrtion of wter t the inlet NO 3 concentrtion of the wter t the outlet Percentge of nitrte removl (%) = [NO 3 concentrtion of wter t the inlet NO 3 concentrtion of the wter t the outlet/ NO 3 concentrtion of the wter t the inlet] x 100 Height: circumference rtio = Dimeter/ Height Time series were subjected to regression nd correltion nlyses using sttisticl pckges for nlyzing the interction mong the tretments. Differences of tretment men pir were performed using Duncn New Multiple Rnge Test (DMRT) t P<0.05. Results nd Discussion Experiment 1 The key wter qulity prmeters of inlet wter in Experiment 1 re shown in Tble 1. They were found to be stisfctory for growth of lettuce hydroponic plnts in ll tretments (Rkocy et l.,

3 P. Sreejriy et l. / Turk. J. Fish. Aqut. Sci. 16: (2016) 313 Vlve Treted fish c (1) (2) (3) Figure 1. Schemtic representtion of the ARDA quponic system consisting of 3 components. (1) = Four fish rering tnks (2) = Biofilter; one biofilter tnk, two solid removl tnks, eight filter tnks with nets (3) = Hydroponic tnks; in this experiemnet, six hydroponic tnks were used = Wter inlet nd smpling point b = Wter outlet nd smpling point c = Sump = Vlve. Tble 1. Minimum nd mximum temperture, ph, DO nd conductivity t the wter inlet during Experiment 1 Prmeter Morning (MinMx) Evening (MinMx) Temperture ( o C) DO (mg L 1 ) ph Conductivity (µs cm 1 ) ; DeLong et l., 2009; FAO, 2014). Ammoni (NH 3 ) in the inlet wter remined stble during the first nd second weeks, nd then slightly decresed in the third week. Nitrite (NO 2 ) showed decresinged trend throughout the culture period. In contrst, nitrte (NO 3 ) showed n incresing trend. Orthophosphte (PO 3 4 ) incresed during the first week nd then slightly decresed throughout the culture period. Nitrite (NO 2 ) incresed during the third week then decresed (Tble 2). In this experiment, the weekly verge concentrtions of NO 3 in the outlet wter showed nonsignificnt differences (P>0.05) mongst the tretments. However, NO 3 content in the outlet wter were significntly lower (P<0.05) thn tht of the inlet wter (Figure 2). This indirectly shows tht some NO 3 contents in the wter in the lettuce tnk were bsorbed nd utilized by the lettuce resulting in lower concentrtion compred to the inlet wter. Menwhile, similr content in the inlet wter might be becuse the outlet wter from ech tnk ws polled before pumping bck to the lettuce tnk. Dily NO 3 concentrtions in inlet wter in the morning (07:00h) nd evening (18:00h) reveled liner increse until the end of the experiment (R 2 = 0.90 nd 0.87, respectively; Figure 3). A positive liner reltionship between wter NO 3 contents nd time ws observed, indicting tht ccumultion of NO 3 incresed with time. These dt implied tht the nitrifiction process properly worked, resulting in the increse of NO 3. Lettuce grows well with sufficient uptke of NO 3 (Chng et l., 2013). However, NO 3 contents in wter still incresed, possibly due to its continued production from nitrogenous wste excreted by fish throughout the culture period. Determintion of NO 3 removl cn be wy to evlute NO 3 uptke by plnt. In this study, wter recircultion during nighttime showed n incresing trend of NO 3 (Figure 4) s NO 3 uptke by plnts is t the highest during the night (Nvrro et l., 1998; Fu et l., 2012). Menwhile, recircultion during dytime showed nerly stble trend of NO 3 removl. NO 3 uptke being lower during the dy is possibly due to lettuce efficiently utilizing NO 3 ccumulted during the night nd becuse of photosynthesis. In contrst, decresing trend of NO 3 removl ws observed for the recircultion within 24 hours, s result of the integrtion of the NO 3 removl during the dy nd during night time. The results showed tht the durtion of the wter recircultion did not significntly ffect (P>0.05) lettuce growth in terms of verge height (Figure 5), dimeter (Figure 6), heighttocircumference rtio (Figure 7) nd weight (Figure 8), Since wter

4 314 P. Sreejriy et l. / Turk. J. Fish. Aqut. Sci. 16: (2016) Tble 2. Ammoni (NH 3 ), nitrite (NO 2 ), nitrte (NO 3 ) nd orthophosphte (PO 4 3 ) concentrtion t the wter inlet during the Experiment 1 Week NH 3 (mg L 1 ) NO 2 (mg L 1 ) NO 3 (mg L 1 ) PO 3 4 (mg L 1 ) ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ±0.148 Vlues re mens (± stndrd devition). Figure 2. Nitrte concentrtions t the inlet nd outlet of Tretment 1 (dytime wter circultion), Tretment 2 (nighttime wter circultion) nd Tretment 3 (24 hours wter circultion). Figure 3. Nitrte (NO 3 ) concentrtion t the inlet in the morning (07:00h) nd in the evening (18.00h) during the experiment. recircultion durtion hs no effect on growth nd NO 3 removl, it cn be reduced from 24 hours to hours. This finding is in ccordnce with the result of Shete et l. (2013) on culturing goldfish with spinch wherein wter circultion cn be reduced to 12 hours per dy for economiclly effective quponics production nd my be considered s optimum wter circultion period for goldfish production in the quponic system. The nitrte concentrtion in the sp of the lettuce lef midribs were 2260, 2440 nd 2470 mg kg 1 NO 3 FW for T1, T2, nd T3, respectively, nd there were no significnt differences mong tretments (P>0.05). These vlues met stndrds of the EU mximum

5 P. Sreejriy et l. / Turk. J. Fish. Aqut. Sci. 16: (2016) 315 Figure 4. Percentge of NO 3 removl t the outlet t dytime (T1), nighttime (T2) nd 24 hours (T3; control) wter recirculting dily during Experiment 1. permissible lef nitrte concentrtions of vegetble products (Commission Regultion (EC) No 1881/2006, 2006; Cometti et l., 2011; Liu nd Yng, 2012). Experiment 2 The key wter qulity prmeters of inlet wter in Experiment 2 re shown in Tble 3. They were found to be suitble for hydroponic plnts in ll tretments (Rkocy et l., 2006; DeLong et l., 2009; FAO, 2014). The concentrtions of NH 3, NO 2 NO 3 nd PO 4 3 decresed during the first week, nd then incresed grdully until the end of experiment (Tble 4). The growth prmeters of lettuce re shown in

6 316 P. Sreejriy et l. / Turk. J. Fish. Aqut. Sci. 16: (2016) Figure 5. Averge height of lettuce in Experiment 1. Figure 6. Averge dimeter of lettuce in Experiment 1. Tble 5. Averge weight, dimeter nd heighttocircumference rtio of lettuce with no shding (S3) nd 30% shding (S2) were significntly higher thn with 60% shding (S1) (P<0.05). The height of lettuce in S1 nd S2 ws significntly higher thn lettuce in S3 (P<0.05). In this study, 60% shding showed n inhibitory effect on lettuce growth. Lettuce incresed its height to seek the sun light, which incresed the height to circumference rtio of the plnt. Most frmers use shding to protect crops from excessive temperture nd solr rdition (Demšr, 2004; Sikw, 2010; Fu et l., 2012) tht negtively ffect plnt qulity, prticulrly lefy vegetble, by inducing scorch ppernce (Hunter nd Burritt, 2005). Shding with 60% nd 30% incresed the nitrte concentrtions in the sp of the lettuce lef midribs significntly. They were 1910±84.9, 1630±70.7 nd 1220±82.0 mg kg 1 NO 3 FW for the 60%, 30% nd the control no shding tretments, respectively. Similr results of incresed NO 3 content in the plnt sp with incresed shding were observed by He et l. (2011) nd Fu et l. (2012) but this study showed tht the vlues obtined with ll shding rtes tested were still in ccordnce with the EU mximum permissible lef nitrte concentrtions in lef vegetbles (Commission Regultion (EC) No 1881/2006, 2006; Cometti et l., 2011; Liu nd Yng, 2012). Conclusions This study llowed the definition of vrious technicl prmeters very importnt for commercil opertion of quponic systems: (1) First of ll, it showed tht quponic technology produced vegetbles s sfe for humn consumption s those produced by more trditionl frming systems in terms of nitrte content. Indeed, this nutrient s concentrtion in the sp of the lettuce leves midrib in both experiments were lwys in ccordnce with the EU mximum permissible lef

7 P. Sreejriy et l. / Turk. J. Fish. Aqut. Sci. 16: (2016) 317 Figure 7. Averge height: circumference rtio of lettuce in Experiment 1. Figure 8. Averge weight of lettuce in Experiment 1. Tble 3. Minimum nd mximum temperture, ph, DO nd conductivity t the wter inlet during Experiment 2 Prmeter Morning (MinMx) Afternoon (MinMx) Temperture ( o C) DO (mg L 1 ) ph Conductivity (µs cm 1 ) nitrte concentrtions in vegetbles for humn consumption. (2) Another mjor finding ws tht it is possible to get the sme performnce when reducing the durtion of the pumping for wter recircultion to 11 to 13 hours, either during dytime or nighttime. Considering the cost of energy in some res such s the remote Reunion islnd, s well s the importnce of pumping in the opertion costs of quponic systems, this open the wy to significnt economic svings nd higher profitbility. The choice between dytime or nighttime however depends on the possible differentil price of energy during the dy nd night. (3) Finlly, it llowed to determine tht 30% shding ws the optiml shding rte for ensuring lettuce lef qulity nd consumer sfety without ffecting its growth. However, shding incresed the nitrte concentrtion in plnt, lthough it lwys remined sfe for humn consumption.

8 318 P. Sreejriy et l. / Turk. J. Fish. Aqut. Sci. 16: (2016) Tble 4. Ammoni (NH 3 ), nitrite (NO 2 ), nitrte (NO 3 ) nd orthophosphte (PO 4 3 ) concentrtion t the inlets during Experiment 2 Week NH 3 (mg L 1 ) NO 2 (mg L 1 ) NO 3 (mg L 1 ) PO 3 4 (mg L 1 ) ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ±0.220 Vlues re mens (± stndrd devition). Tble 5. Averge weight, height, dimeter nd heighttocircumference rtio of lettuce t the end of Experiment 2 Tretment Weight (g) Height (cm) Dimeter (cm) Height: Circumference rtio 60% shding ±2.3 b 18.0± ± 0.7 b 1.3±0.0 b 30% shding ± ± ± ±0.0 No shding 242.0± ±0.3 b 26.3± ± 0.0 Vlues re mens (± stndrd devition). Vlues showing common superscript re not significntly different (P>0.05). Acknowledgements This study ws supported by the Centre de Coopértion Interntionle en Recherche Agronomique pour le Développement (CIRAD) nd the Assocition Réunionnise pour le Développement de l'aquculture (ARDA) fish frming experimentl reserch sttion t l Etng Slé L Réunion, Frnce References APHA (Americn Public Helth Assocition) Stndrd Methods for Exmintion of Wter nd Wstewter, 20th edition. Americn Public Helth Assocition, Americ Wter Work Assocition nd Wter Pollution Control Federtion.Wshington, DC, USA. Broiller, J.F. nd D'Cott, H Environment nd sex determintion in frmed fish. Comprtive Biochemistry nd Physiology Prt C, 130: Blidriu, F. nd Groze, A Incresing the economic efficiency nd sustinbility of indoor fish frming by mens of quponicreview. Animl Science nd Biotechnologies, 44(2): 18. Chng, A.C., Yng, T.Y. nd Riskowski, G.L Ascorbic cid, nitrte concentrtion reltionship to the 24 hour light/drk cycle for spinch grown in different conditions. Food Chemistry, 138: Cometti, N.N., Mrtins, M.Q., Bremenkmp, C.A. nd Nunes, J.A Nitrte concentrtion in lettuce leves depending on photosynthetic photon flux nd nitrte concentrtion in the nutrient solution. Horticulture Brsileir, 29: Commission Regultion (EC) No 1881/ Commission Directive 2006/1881/EC of 19 December 2006, setting mximum levels for certin contminnts in food stuffs. Officil Journl of the Europen Communities, L364: DeLong, P.D., Losordo, M.T. nd Rkocy, J.E Tnk Culture of Tilpi. SRAC Publiction, No. 282, Texs, USA, 7 pp. Demšr, J., Osvld, J. nd Vodnik, D The effect of lightdependent ppliction of nitrte on the growth of eroponiclly grown lettuce (Lctuc stiv L.). Journl of the Americn Society for Horticulturl Science, 129(4): FAO Smllscle quponic food production. Integrte fish nd plnt frming. FAO Fisheries nd quculture technicl pper No Food nd Agriculture Orgniztion of the United Ntions Rome, Itly, 262 pp. Fu, W., Li, P., Wu, Y. nd Tng, J Effects different light intensities on ntioxidtive enzyme ctivity, qulity nd biomss in lettuce. Horticulturl Science (Prgue), 39(3): God, A.M.A., Ess, M.A., Hssn, M.S. nd Shrwy, Z Bio economic fetures for quponic systems in Egypt. Turkish Journl of Fisheries nd Aqutic Sicences, 15 (3): doi: / ; He, J., Cheok, L. nd Qin, L Nitrte ccumultion, productivity nd photosynthesis of temperte butter hed lettuce under different nitrte vilbilities nd growth irrdinces. The Open Horticulture Journl, 4: Hunter, D.C. nd Burritt, D.J Light qulity influences the polymine content of lettuce (Lctuc stiv L.) cotyledon explnts during shoot production in vitro. Plnt Growth Regultion, 45: doi: /s z ; Klinger, D. nd Nylor, R., Serching for solutions in quculture: Chrting sustinble course. Annul Review of Environment nd Resources, 37: doi: /nnurevenviron ; Ling, J. nd Chien, Y Effects of feeding frequency nd photoperiod on wter qulity nd crop production in tilpiwter spinch rft quponic system. Interntionl Biodeteriortion & Biodegrdtion, 85: doi: /j.ibiod ; Liu, K.W. nd Yng, Q.C Effect of shortterm tretment with vrious light intensities nd hydroponic solution on nitrte concentrtion of lettuce. Act Agriculture Scndinvic, Section B Soil & Plnt Science, 62(2): doi: / ; Love, D.C., Fry. J.P., Li, X., Hill, E.S., Genello, L.,

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