HYDROPONIC CULTURE OF TOMATO AND GERBERA AT DIFFERENT SUBSTRATES Manios V.I. Abstract Papadimitriou M.D. Kefakis M.D. In our Institute several experimental hydroponic cultures were carried out in different substrates. Data obtained indicate that the pumice from the Greek island of Nisyros could be used as a substrate for hydroponic culture of tomato and gerbera. 1. Introduction In Crete there are about 1700 hectares of commercially grown greenhouse crops. From these only five hectares of tomato are grown on soilless culture, and more specifically on rockwool. In addition, several experimental hydroponic cultivations were carried out under different substrates or by using the Nutrient Film Technique (N.F.T.). These initial experiments aimed at determining the suitability of some localy available, less costly materials, as soilless culture substrates and developing cultivation systems for the growers using such materials. 2. Material and methods The substrates used in these experiments are the following: - "sieved pumice", from the Greek island of Nisyros, from 1.3 to 7 mm. - "washed pumice", of the above type. - a mixture of sieved pumice (85%) and light peat (15%) - perlite with a particle size between 1 to 5 mm. - a mixture of perlite (85%) and peat (15g). - rockwool. These substrates were used once, twice, or three times. The physical and physicochemical properties of pumice, perlite, light peat and their mixture are presented in Table 1 (De Boodt and Verdonck 1972; Sonneveld et al., 1974). These data indicate that the total pore space and the ph of pumice are nearly the same as in perlite. The E.C. of pumice is, about 10 times more than that of perlite. After sieving or washing, it is reduced by about 35%. The "water-release" curves of the above subtrates are presented in Figure 1 (Verdonck, 1983). They indicate that the pumice substrates hold more water than the perlite in different suctions. The pumice and perlite substrates were placed in plastic bags made of white and black polyethylene film. The bags were 90 cm long by 30 cm wide and their total capacity was 30 It. The slabs of rockwool (the commercial brand Grodan) were rolled in polyethylene film. The slab dimensions for tomato were 90x20x 7,5 cm and for gerbera xl2x 10 cm. Acta Horticulturae 8, 1995 Soilless Cultivation Technology for Protected Crops 11
Two tomato plants of the cultivar Dobito or Caruso or four gerbera plants of the cultivar Ximena were planted in each bag or in a rockwool Grodan slab. The experiments with tomato were carried out in an unheated greenhouse covered with polyethylene film, while the experiment with gerbera was carried out in a heated glasshouse. Irrigation and fertilizers were applied by a nutrient solution prepared in a tank (Sonneveld and Welles., 1984). The distribution of the nutrient solution to the plants was effected by a using pump, without recycling. The experiments with tomato plants were fertirrigated with solution provided using drippers of x lt/hour for two minutes every 30 minutes and with gerbera for two minutes every one or two hours, depending on the weather and stage of plant development. 3. Results The data of Table 2 indicate that there is no significant statistical difference among substrates with respect to the yield of tomato cultivar Dobito. However, the substrates of pumice and perlite produced larger quantities of smaller fruits per plant. The data of Table 3 indicate that tomato cultivar Caruso yield was the same in all substrates used for second time. When substrates were used for third time, the perlite-peat mixture was better. Comparing all substrates, sieved pumice and perlite-peat mixture proved to be the best. Data of Table 4 indicate that there was no significant statistical difference among the substrates with respect to the yield and the quality of the flowers of gerbera cultivar Ximena. It is concluded that the pumice from the Greek island of Nisyros can be used as a substrate for the hydroponic cultivation of tomato and gerbera. Also it is necessary to continue the experiments on this subject in order to find the most appropriate particle sizes of Nisyros pumice for these crops. Acknowledgements The experiments were carries out with the technical support of the students Papachristou P., Jinoudis G., and Papaioannou A., during their industrial practice which was carried out at the Laboratory of Substrate Biotechnology at the T.E.I, of Heraklion. References De Boodt, M. and Verdonck, O., 1972. The physical properties of the substrates in horticulture. Acta Horticulturae, 26 : 37-44. Sonneveld, C., van den Ende J. and van Dijk P.A., 1974. Analysis of growing media by means of a 1 : 1 1/2 volume extract. Comm.in science and plant analysis, 5 (3) : 183-202. Sonneveld, C. and Welles. G.W.H. 1984. Growing vegetables in substrates in the Netherlands. ISOSC Proceedings, pp 613-632. Verdonck, O., 1983. New developments in the use of grated perlite in horticultural substrates. Acta Horticulturae, 150 : 575-582. 12
Table 1 - Physical and physical-chemical properties of Pumice, perlite, light peat and their mixtures. Materials Bulk Total PH E.C. of density pore substrates (g/cm3) space(%) (ms/cm) 1. Nlsyros pumice (raw meterial) 0.88 71. 7.31 0.48 2. Sieved pumice (l,3-7mm) 0.62 76. 7.25 0.31 3. Washed pumice 0.63 75.53 7.28 0.34 4. Perlite 0.11 72.00 7.12 0.03 5. Light peat 0.09 92.32 4.96 0.15 6. Sieved pumice 85% + L.peatl5% 0.52 79.36 7.12 0.37 7. Perlite 85% + L.peat 151 0.09 85. 6.26 0.05 BO 20 9 1 O 4 2 4.2-20.6 0' O nit n 23.2 20 Suction (cm HjO) O E2 EKU EK n : Perlite T : Light peat n+t : Perlite 85% + Light peat 15% EH : Washed pumice EK : Sieved pumice EK+T : Sieved pumice 85% + Light peat 15% Figure 1 - Water release curves of pumice, perlite, and light peat.
Table 2 - Yield 1 of a hydroponic culture of tomato (cv Dobito) on several substrates in growth bags. Fruits Yield Fruit Substrates (nwnber/plant) (Kg/plant) Weight (g) 1. Sieved pumice 2 % 37.50 3 a 4.13 a 109.67 a b 2. S.pumice 851 + L.peat 15!(v/v) 36.82 a 3.92 a 106.38 b c 3. Perlite! 36.92 a 3.70 a.00 c 4. Perlite 85% + L.peat 15%(v/v) 35.96 a b 3.79 a 105.20 b c 5. Perlite 851 + L.peat 15%(v/v) (2nd time) 31.86 b 3.75 a 117.56 a 6. Rockwool 34.42 a b 3.84 a 111.98 a b 1. Yield (20.5.93-10.8.93). 2. Sieved pumice (l,3-7mm) 3. Means followed by the same letter are not statistically different at 5% level. Table 3 - Total yield of a hydroponic culture of tomato (cv Caruso) on several substates in growth bags. Substrates Yield 1 2nd use (Kg/plant) 3rd use 1. Sieved pumice 2 5.. 56 3: a A 4.,91 a b A B 2. S.pumice 85% + L.peat 15% (v/v) 4..59 a AB 4..90 a b A B 3. Perlite 5..03 a AB 4..95 a b A B 4. Perlite 85% + L.peat 15% (v/v) 5..38 a AB 5..87 a A 5. Rockwool 4..88 a AB 3..98 b B 1. Yield (26.6.93-9.9.93). 2. Sieved pumice (l,3-7mm). 3. Means followed by the same letter are not statistically different at 5% level. 14
Table 4 - Yield of a hydroponic culture of gerbera (cv Ximena) on several substrates in growth bags. Flowers 1 Stem Flower Substrates (number/ length diameter plant) (cm) (cm) 1. Sieved pumice 2 % 11. 3 a 50..56 a 9..81 a 2. Washed pumice % 11.52 a 48..59 a 9,. a 3. S.pumice 85% + L.peat 15% (v/v) 13.06 a 50..67 a 9..52 a 4. Perlite % 10.31 a 47..87 a 9..71 a 5. Perlite 85% + L.peat 15% (v/v) 11.45 a 52..84 a 9..72 a 6. Rockwool 10.81 a 48..47 a 9..72 a 1. Sixteen crops in 88 days, from 2/5/92 to 29/7/92. 2. Sieved pumice (l,3-7mm). 3. Means followed by the same letter are not statistically different at 5% level. 15