PRECOCITY, PLANT PRODUCTIVITY AND FRUIT QUALITY OF STRAWBERRY PLANTS GROWN IN SOIL AND SOILLESS CULTURE. Greece

Transcription

1 PRECOCITY, PLANT PRODUCTIVITY AND FRUIT QUALITY OF STRAWBERRY PLANTS GROWN IN SOIL AND SOILLESS CULTURE Paraskevopoulou-Paroussi G. Grafiadellis M. N.AG.RE.F. Agric. Res.Center of N. Greece Department of Horticulture Thermi, Thessaloniki Greece Paroussis E. N.AG.RE.F. Soil Science Institute Georgiki scholi Thessaloniki Greece Abstract The response of two day-neutral strawberry cultivars, Brighton and Selva, cultivated in plastic pots filled with soil mixture and hydroponically in vertical plastic bags filled with perlite was studied at the Agricultural Research Center of Northern Greece. The purpose of this study is to investigate the performance of the cultivars grown hydroponically regarding precocity, productivity, fruit quality and some vegetative characteristics which are correlated with them, in order to identify the most suitable cultivar for out-of-season production in soilless cultivation. Cv. Selva gave the highest marketable (259 g/plant) and total (315 g/plant) yield in soilless culture, while in soil the yield of this cultivar was significantly higher (382 g/plant and 467 g/plant, marketable and total yield, respectively). However, because of the higher plant density per stremma in the soilless culture, the estimated yield was about 6207 Kg/stremma marketable and 7571 Kg/stremma total yield, while in soil culture it was about 1915 Kg/stremma marketable and 2332 Kg/stremma total yield. Cv. Selva produced the larger fruits of extra (>20 g/fruit) and A (>14 g/fruit) categories, 53 % in soilless and 49 % in soil, while Cv. Brighton produced more fruits of the B (>9 g/fruit) category (37 %) and only 30 % of E+A categories. The greatest number of leaves, fresh and dry weight of plants was observed in cv. Selva. A decrease of leaf number, fresh and dry plant weight and crown number per plant was observed in the lower part of the vertical bags in the hydroponic cultivation. Soluble solids content was greater in the fruits of cv. Brighton (8.33) and firmness was higher in the fruits of cv. Selva (1.31). Cultivation technique did not affect the fruit quality characteristics significantly. 1. Introduction Strawberries are attractive fruits which ensure a high price if they are produced during winter time. Traditionally, the crop is grown outdoors or under plastic tunnels without heat in Northern Greece; as a result, the production period is short and the market is oversupplied in May. There is an increasing interest in soilless culture especially for the vertical sac system of hydroponic culture for strawberries, because it makes better energy utilization and more efficient use of the greenhouse volume, resulting in higher yield per unit area (Tropea, 1976; Manios et al., 1985). Moreover, by growing strawberries hydroponically, soil problems such as poor structure, drainage, salt accumulation and soil fumigation can be avoided. However, there are some problems related to plant productivity and fruit quality depending on the cultivar, the position of the plant on the vertical bag (Vassilakakis et al., 1991), and the climatic conditions (light intensity, temperature). Various cultivars (Kapylov and Pupova, 1985), substrates (Manios, 1985; Sarooshi, 1987) and modifications of the system (Morard, 1985; Pages et al., 1983) have been Acta Horticulturae 408, 1995 Soilless Cultivation Technology 109 for Protected Crops

2 tested until now. However, it is necessary to assess the potential yield and quality of the most important and recently introduced cultivars, under the local environmental conditions in relation to season and the cultivation technique. In addition, since competition is increasing for markets and top quality produce is demanded all year round by the consumers, it has become evident that not only crop production must be adequate but also the quality of the fruit must be improved. Yield and quality of strawberries are related to environmental conditions (Dijkstra, 1985, Vassilakakis et al., 1989), cultivar (Scaik, 1986) and the medium in which the plants are grown (Vassilakakis et al., 1991 ). Our study was designed to evaluate two day-neutral strawberry cultivars to assess their yield and quality in relation to the method of culture (soil-soilless) in order to identify the most suitable cultivar for soilless cultivation under the climatic conditions of Northern Greece 2. Materials and methods Vertical plastic bags 2.0 m long and 0.16 m wide, filled with perlite, were installed at intervals of 0.80 x 1.0 m, about 1000 bags/stremma (1000 m2), in a heated greenhouse with minimum air temperature of 12 C for the hydroponic cultivation of strawberry plants (24 plants/bag, 24,000 plants/str.). Nutrient solution was released with two drippers, capacity 4 1/h/dripper, through feeding pipes into the upper and middle part of the bags. Holes were made in the bottom of the bags to assure drainage. Also, strawberry plants were grown in soil mixture in plastic pots, 5 1/pot, in double rows at a distance on and within the rows 40 cm, and between the double rows 50 cm (about 5,000 plants/str.). Two cultivars, Brighton and Selva, were used to evaluate their productivity and fruit quality. The plants were set in August, 20 and the greenhouse was covered with double plastic polyethylene in October. The experimental design was a complete block with 3 replicates and 4 bags/replicate in the hydroponic cultivation and two rows of twenty four plants/replicate in the soil. The following records were taken for each experimental plot: i. Fruit weight at each harvest, according to which the fruits were sorted out in the following categories: >20 g/fruit (E), g/fruit (A), 9-14 g/fruit (B), 5-9 g/fruit (C), <5 g/fruit (D), malformed (M) and rotten (R). ii. Growth parameters (number of leaves, crowns, plant fresh and dry weight) during the growth period and at the end of harvesting. iii. Percentage of soluble solids, skin colour (L) and firmness (Kg) of the fruits. iv. Temperature, light intensity and relative humidity of the greenhouse (Fig. 1,2,3). Also, the internal bag substrate temperature which was kept during day at about C in the top half of vertical bags and at C in the bottom half, moisture and light intensity (lux) profile along the bag on selected days (Fig. 5). 3. Results and Discussion 3.1. Precocity - Total yield Three production periods (very early, early and late) were observed. The first, with a peak in November, lasted from November to January. The second, during which the highest peak was observed in March, lasted from February to April and the third, peaked in May, lasted until June 6th (Fig. 4, a). "Selva" produced earlier fruits, with a peak during the 110

3 first period, about 25% of the total marketable production, while during the second period both cultivars produced more than 50% (Fig. 4, b). Also, "Selva" was more productive than "Brighton", both in soil and soilless culture (Fig. 4, c), with 382 g/plant and 259 g/plant total marketable yield, respectively (Table 1). That means 1915 kg/str. for the plants grown in soil and 6207 kg/str. in soilless vertical bag hydroponic culture (Table 1) since this technique allows for a higher plant density (Manios et al., 1985; Tropea, 1976). The plants of cv. Selva either in soil or soilless culture were more vigorous, with more crowns and greater fresh and dry weight/plant compared to "Brighton". Also, the plants in the pots were more vigorous compared to the plants in the vertical bags (Table 2). This difference in plant vigour resulted in the higher yield/plant, since more vigorous plants produce more fruits (Jahn and Dana, 1966, 1970). Plant size, as it is recorded by the number of leaves, crowns, fresh and dry weight, was affected by the cultivation technique (soil-soilless), and by the plant position and orientation along the bag (Fig. 6, Table 2). The plant vigour in the top half of the vertical bags and in the pots is due, most probably, to the higher temperature (>15 C during day time) which was recorded at that level (data not shown) and the higher light intensity (Fig. 5), which in turn increases temperature (Marfa et al., 1986), because at higher temperature there is better uptake of nutrients (Massantini, 1970; Cornillon, 1988). Moreover, the higher light intensity affected plant vigour and yield per plant, since shading decreases crown and leaf weight (Ferree and Stang, 1988), while high light intensity increases the number of flowers and fruit set (Smeets, 1980) Fruit quality Fruit size The highest percentage of the total marketable production was from the large fruits (E+A+B) for "Selva" and "Brighton", either in soil or soilless culture. "Selva" produced more fruits of the E and A categories (53% in soilless and 49% in soil) than "Brighton", which produced more fruits of the B category (37%) and only 30% of the E+B categories (Fig. 7). Fruit size was not affected by the cultivation technique siqnificantly Flesh firmness (F.F) "Selva" produced firmer fruits ( kg) compared to "Brighton" ( kg) (Table 3), depending on cultivar (Ourecky and Bourne, 1968). Firmness was higher during winter and lower during spring (data not shown) Colour (L) There was not a significant difference in colour between the two cultivars in soil or soilless cultivation (Table 3) Soluble solids (SS) Soluble solids content was higher in the fruits of "Brighton" 8.5 % in soilless and 9.2 % in soil - compared to those of "Selva" 7.2 % and 7.62 %, respectively (Table 3). The position of the plants in the bag affected SS content of the fruits. It was lower in the fruits at the bottom half of the bag because of shading (Dijkstra, 1985, Vassilakakis et al., 1991). ill

4 4. Conclusions Cv. Selva performed better either in soil or soilless culture compared to cv. Brighton. It was more productive and it produced more fruits in a shorter time. Fruit colour was not significantly different between the two cultivars in both cultivation techniques. Cv. Selva produced firmer fruits, while a higher content of soluble solids was observed in the fruits of cv. Brighton. References Cornillon, P., Influence of root temperature on tomato growth and nitrogen nutrition. Acta Hort. 229: Dijkstra, J., Preliminary results of taste experiments and determination of soluble solids and acids in the strawberry. Proceedings of E.E.C. Agro-food Workshop, Dublin, September Ferree, D. C. and Stang, E.J., Seasonal plant shading, growth and fruiting in 'Earliglow' Strawberry. J. Amer. Soc. Hort. Sci. 113 (3): Jahn, L.O. and Dana, M.N., Fruiting and growth of the Strawberry plant. J. Amer. Soc. Hort. Sci. 88: Jahn, L.O. and Dana, M.N., Growth relationships in the strawberry plant. J. Amer. Soc. Hort. Sci. 95(6): Kapylov, V.I. and Pupova, L.N., Strawberry cultivars for vertical culture. Sadovodsvo, Vinogradastro i Vinodelie Moldavii 9:31-32 (English abstract). Manios, V.I., Kitsotakis, K.G., and Papadimitriou, D.M., Vertical cultivation of strawberries in greenhouse on substrate of pumice-stone with several composts. Agric. Res. 9(l):52-63 (in Greek). Marfa, O., Ramos, T., Jover, M. and Save, R., Vertical bag system used for mother foliage pot plants culture. Effects of substrate. Acta Hort. 178: Massantini, F., Hydroponic culture of strawberries Atti. iv Congr. Naz. Delia Fragola, Cesena: (in Italian). Morard, P., Nutritional control of strawberries hydroponically grown in vertical columns using percolate analysis. ISOSC Proc Ourecky, K. and Bourne, M.C., Measurement of strawberry texture with an Instron Machine. Am. Soc. Hort. Sci. 93: Pages, O.M., Prado, C.C. and Saudela, M.T., Strawberry sack culture on steep gradient soil. Evaluation of the substrate and the sack type and position on the slope. Acta Hort. 150: Sarooshi, R., Hydroponically growing strawberries. In : Hydroponics Workshop. Salamander Bay, 16-18th March, 1987 NSW. 93 pp Scaik, A.C.R., Fruit storage for distant market C.E.C. Workshop. Thessaloniki, Greece, November Smeets, L., Effect of light intensity on forcing of the strawberry cultivar Glasa Scientia. Hort. 13: Tropea, M., Nutrient control in a new vertical hydroponic system. L' Italia Agricole 113. (in Italian). Vassilakakis M., Dogras, C. and Ritos, N., The effect of chilling, photoperiod and light intensity on productivity and fruit quality of strawberries. 14th Annual Meeting of Greek Society for Hort. Science, October (in Greek). Vassilakakis, M., Dogras, C., Vlachonasios, C. and Mastrokostas, M.,1991. Out of season strawberry production under glasshouse conditions. 15th Annual meeting of Greek Society for Hort. Science, November (in Greek). Acknowledgments This research has been supported financially by the CAMAR EC program DGVI-PL and the National Agricultural Research Foundation of Greece (N.AG.RE.F.). 112

5 Table 1. Early marketable and total yield of two strawberry cultivars grown in soil and hydroponically vertical culture in g/plant and Kg/stremma. g/plant Early Total Marketable Marketable + Marketable Marketable + Cultivar Treatment unmarketable unmarketable Selva Soilless 211 b 256 b 259 b 315 b z Brighton Soilless 168 c 244 b 199 c 296 b Selva Soil 342 a 418 a 382 a 467 a Brighton Soil 205 b 321 b 224 b 360 b Kg/str. Selva Soilless 5054 a 6151 a 6207 a 7571 a Brighton Soilless 4032 b 5860 a 4764 b 7102 a Selva Soil 1709 c 2092 b 1915 c 2332 b Brighton Soil 1024 c 1606 b 1120 c 1800 b z Mean separation by Duncan's Multiple range test, p=0.05. Table 2. Mean fresh and dry weights of strawberry plants and number of crowns in relation to cultivation technique and their position in the column in soilless culture. Cultivar Treatment F.W./plant D.W./plant N of crowns (g) (g) Selva Soilless top b b 6,.33 a z»» bottom c 12,.00 c c Brighton Soilless top c 12,.24 c be»» bottom c 12,.95 c be Selva Soil 86,.67 a 34,.27 a a Brighton Soil a 32,.00 ab ab z Mean separation by Duncan's Multiple range test, p=0.05. Table 3. Effect of cultivar and cultivation technique on fruit colour, firmness and soluble solids content. Cultivar Treatment Col our (L*) Fi rmness (Kg) Soluble Solids (%) Sei va Soilless top a 1.31 a 8.2 a z»» bottom a 1.31 a 6.2 b Brighton Soilless top a 0.58 b 9.2 a >>» bottom a 0.58 b 7.8 a Selva Soil a 1.28 a 7.7 ab Brighton Soil a 0.62 b 9.2 a z Mean separation by Duncan's Multiple range test, p=

6 M. M. Minimum o Maxi - night day mum Months Fig. 1.-Mean day,night, minimum and maximum temperature^in the experimental greenhouse. 80 T Months Fig. 2_Mean relative humidity in the experimental greenhouse. Months Fig. 3 Monthly light intensity distribution in the greenhouse during sunny and cloudy days. 114

7 BrSIess BrSoil SeSless 0 Sesoil Marketable yield Cumulative marketable yield 5000 S S Fig. 4. Yield distribution and cumulative yield (Kg/str., percentage) of two strawberry cultivars in soil and soilless culture.

8 bottom top _ x = > 8000 s 6000 c ~ 4000.c 2000 o> 13 0 W N 1/2/ am x 3 <o C o.c OS W N 1/2/ am x 3 M c 0) c x: O) W N S 1/2/ am Fig. 5-Variation of light intensity at different levels (top-bottom) and orientation (S,E,W,N) of the vertical bags in soilless culture of strawberries during morning in winter. 116

9 TOD 23/11/1992 Bottom Brighton SW 16/6/1993 Brighton Fig. 6. Number of leaves and crowns of strawberry plants as related to their position and orientation on the vertical bag of hydroponic culture BrSless BrSoil SeSless SeSoil Fig. 7. Total yield per fruit category by cultivar as affected by cultivation technique (soil and soilless). 117