Green-Pepper Fertigation in Soilless Culture

Transcription

1 Green-Pepper Fertigation in Soilless Culture M. García Lozano, I. Escobar and J.J. Berenguer Estación Experimental La Nacla Caja Rural de Granada Circunvalación, Granada Spain Keywords: substrates, nutrient solutions, greenhouse, drip irrigation. Abstract Green peppers, Capsicum annuum, were cultivated in perlite for two consecutive years in an unheated greenhouse on the coast of Granada (Spain). Both crops were begun in spring, the traditional season for green peppers in the zone. The first year, four different K levels in the nutrient solution were maintained constant throughout the growing cycle. Only the treatment with 1.5mmol/l of K + gave less yield than the rest, although the treatment with 3 mmol/l of K + had developmental problems in the early growth phases before recuperating and providing statistically the same yield as the other two treatments (6 and 4.5 mmol/l of K + ). The second year, two treatments were applied. For the first, 5 mmol/l of K + were applied over the entire growth cycle, an intermediate quantity with respect to the two treatments that proved best the first year. In the second treatment, the same solution was used until before the first harvest, when the amount was reduced to 2.75 mmol/l of K + until the end of the season. In this second year, no differences were found in yield between the two treatments. INTRODUCTION Green pepper, Capsicum annuum, has been one of the most difficult crops to adapt to cultivation conditions in southern Spain. In the mid-1980s, when the first peppers were grown with nutrient solutions recommended by some technical advisers from Holland (7 or more mmol/l of K+), the resulting peppers were thick-walled, small and easily susceptible to blossom end rot. These drawbacks were overcome, apparently, by reducing the amount of K, but comparative tests were not made (Escobar, 1993). Here we explore whether fertigation can be used to improve these weak points and boost commercial yield in pepper cultivation, as achieved previously in tomato growing. (García Lozano et al., 2002). MATERIALS AND METHODS The experiment was conducted in an open-frame greenhouse oriented E-W, constructed with galvanized tubing and covered in clear three-layered plastic. The interior space consisted of three sections of equal area (6 m wide x 37 m long) with a gabled roof above each section. The walls were 4 m high, with the apex of the gable 5.5 m from the soil. The pitch of the roof was 27º. Automatic ventilation was provided by folding sections on the roof and by rolling up the plastic on the lateral studs. The perlite used (commercial name B12), made by Europerlita Española S.A., had a grain size of 0.5 to 5.0 mm. The injection system automatically monitored CE (electrical conductivity) and ph. In the test, one drip emitter was used every square meter of cultivated surface area at a flow rate of roughly 3 litres h -1 with 1 atm of pressure. Independent irrigations systems were used for each treatment. The first year, the variety cv. Ziggy- was planted on 7/03/2003. The first harvest was on 23/05/2003 and the last on 22/08/2003. For the second season, the variety was cv.litron, planted on 16/03/2004, harvested from 9/06/2004 to 12/08/2004. The first year, the planting scheme was 2*0.5 m 2 at a density of 2 plants m 2, while for the second season, the scheme was 1.5*0.3 m 2 at a density of 3 plants m 2. In all cases, the cultivation techniques and pesticides applied were routine for the area. Daily, over the growth cycle of the crop, the drainage solutions were measured manually for volume, ph, and EC. The ions present in the drains and the nutrient solution were chemically analysed monthly. Proc. IS on Soilless Cult. and Hydroponics Ed: M. Urrestarazu Gavilán Acta Hort. 697 ISHS

2 The experimental design was complete random block, with four treatments and three replicates the first year and with two treatments the second year. Physically, each replicate was comprised of one line of cultivation, and each experimental unit by eleven cultivation sacks, two of which were used as the border effect. At the end of the cultivation, the commercial yield was analysed as well as the data for the nutrient and irrigation parameters. The first year the treatments consisted of the following nutritive solutions applied over the entire crop cycle: A 1 ) 14.5 mmol NO 3 - and 6.0 mmol K +. B 1 ) 13.0 mmol NO 3 - and 4.5 mmol K + (control). C 1 ) 11.5 mmol NO 3 - and 3.0 mmol K +. D 1 ) 10.0 mmol NO 3 - and 1.5 mmol K +. The second year the treatments were: A 2 ) 13.5 mmol NO 3 - and 5.0 mmol K + applied over the entire crop cycle (control). B 2 ) 13.5 mmol NO 3 - and 5.0 mmol K + applied until the first harvest, followed by mmol NO 3 - and 2.75 until the end of the season. RESULTS Analytical Data The results for the two seasons are presented in Tables 1, 2, 3 and 4. All the statistical data show 99% significance. In the first year, the mean results for the analysis of the drainage solutions revealed that, as expected from the design of the treatments, K content declined from A 1 to D 1. The same trend was observed in the nitrate contents and in the CE. The rest of the elements proved to be statistically the same for all the treatments. The differences mentioned above were noted from almost the beginning of cultivation and affected the development of the plants in the C 1 treatment, but especially D 1, which clearly showed K-deficiency symptoms and was very slow in developing compared with treatments A 1 and B 1. These latter two treatments were consistently quite similar, except in the dates corresponding to the evolution of K in the drainage (see Graph 1). At the beginning of the crop cycle the first year, the same irrigation and the same drainage were maintained in the four treatments, regardless of the EC in the drainage. However, given the slow development in the C 1 and D 1 treatments, and the excessively high percentages of drainage, we began to irrigate with adjusted quantities of each treatment in order to maintain the drainage constant. This changed the water use per treatment, as shown in Table 3. In the second year, the mean results of the analysis of the drainage solutions show that in the second phase the K content was far lower in the B 2 treatment, while the contents of the rest of the elements remained statistically the same in the two treatments. Data on Commercial Yield and Quality The data on yield the first year reveal that the D1 treatment produced significantly less than the rest, with the values for the other treatments remaining quite similar (Table 4). Also, non-commercial production was analysed as well as the mean weight of the highest-quality yield, and in no case were significant differences found. The lowest yield with treatment D1 coincides with the results reported for such crops as cucumber and green bean under treatments of excessively reduced fertilizer (García Lozano et al., (2004 (1)). The second year, B2 yielded more than did the other treatment, in addition to saving fertilizer. As we did the first year, other yield and quality indices were analysed without revealing significant differences between the two treatments. DISCUSSION The experimental data for peppers are consistent with those that we found for tomato, bean, cucumber and melon, showing that even in soilless crops the margins of treatment are broad and that minor changes in irrigation or nutrient solution do not tend to result in great improvement or great damage (García Lozano et al., 2002, 2004 (1) and 2004 (2)). The first year, the management of the fertigation used as control (treatment B 1 ) was found to give very acceptable results. In this respect, we should emphasize that it maintained the same yield as the A 1 treatment with less fertilizer application. Although treatment C 1 544

3 might appear to be good, with a lower water and fertilizer expenditure than in treatment B 1, we should take into account first of all the above-mentioned developmental problems at the beginning of the cultivation and secondly that, although significant differences were not found with respect to B1, it is true that the latter gave better results. In view of the yield results for the first year, we tested the possibility of reducing the fertilizer concentration during the yield period that is, to change to treatment C 1 and even D 1. Therefore, we undertook the second-year experiment, the results of which confirmed our suspicions that costs could be curbed without reducing, and even boosting, yield. These results were in fact supported by our results with tomatoes (García Lozano et al., 2002) and cucumbers and green beans (García Lozano et al., 2004(1)).. It might be thought that the nitrate levels of C 1 and D 1 influenced yield and the behaviour of these treatments, but in reality, although the values differed from those of A 1 and B 1, all accumulated with respect to the values of the nutrient solution, as opposed to what happened with potassium K. Thus, we believe that this did not affect yield. Similar reasoning can be used with EC. In the second year, these trends are clearer, as there were no significant differences between the nitrate and EC values of the two treatments. Striking differences were found in K content in the drainage between treatments A 1 and B 1 on the one hand and between C 1 and D 1 on the other, as well as between A 2 and B 2 the second year, if we add to this the good results found with C 1 and above all B 2. This should prompt reconsideration to use lower reference values for K in nutrient and drainage solutions than those used in countries in central and northern Europe. ACKNOWLEDGEMENTS We are grateful to Abelardo Martín, supervisor of the experimental plots, for all the hours dedicated to maintaining everything in working order. Literature Cited Escobar, I Cultivo de pimientos en substratos en las condiciones del sudeste español. En: Cultivos sin suelo: hortalizas en clima Mediterráneo. Ediciones de Horticultura. Reus. García Lozano, M., Téllez, M.M., Berenguer, J.J., Escobar and Barcelona, I Noviembre Fertirrigación del tomate en cultivo sin suelo. Resúmenes VI Jornadas de Sustratos de la S.E.C.H. Pag. 40. García Lozano, M., Téllez, M.M., Berenguer, J.J. and Escobar, I. Jornadas de sustratos de la SECH. Madrid, Marzo 2004 (1). Fertirrigación de pepino y judia en cultivo sin suelo. García Lozano, M., Téllez, M.M., Berenguer, J.J.; Escobar and Derio, I. 7-9 Septiembre 2004 (2). Efecto de la fertirrigación y el uso de hormonas en la calidad y el tamaño del melón en cultivo sin suelo. Resúmenes de las IX Jornadas del Grupo de Horticultura de la SECH. Sonneveld, C Items for application of macro-elements in soiless cultures. Acta Hort. 126: Sonneveld, C. and Arnold Bik, R Nutrients solutions for vegetables and flowers grown in water or substrates. Informatiereeks. 69. Tables Table 1. Data for the nutrient solutions for green-pepper cultivation. mmol/l A 1 B 1 C 1 D 1 A 2 B 2 potassium calcium magnesium sodium nitrate phosphate sulphate

4 chloride ph (2) Only data from the second phase are shown. Table 2. Data for drainage in green-pepper cultivation. mmol/l A 1 B 1 C 1 D 1 A 2 B 2 potasium 6.62 a 4.12 b 1.44 c 0.57 d 5.83 a 0.91 b calcium 7.24 a 7.21 a 6.95 a 6.38 a 8.99 a 8.77 a magnesium 3.45 a 3.54 a 3.06 a 2.87 a 3.07 a 2.94 a sodium 4.14 a 4.52 a 4.03 a 3.55 a 3.22 a 3.23 a nitrate 22.6 a 21.2 a 16.7 b 14.3 b 20.4 a 16.0 a phosphate 1.29 a 1.32 a 1.04 a 1.22 a 2.20 a 2.46 a sulphate 1.00 a 0.97 a 1.01 a 1.00 a 3.08 a 3.01 a chloride 5.06 a 5.06 a 4.90 a 4.44 a 3.79 a 3.96 a ph 6.63 a 6.58 a 6.67 a 6.60 a 6.25 a 6.40 a (2)Only data from the second phase are shown. Table 3. Data for daily irrigation of green-pepper cultivation. A 1 B 1 C 1 D 1 A 2 B 2 Water supply CE daily irrigation CE daily drainage 3.55 a 3.31 ab 2.82 bc 2.44 c 2.96 a 3.05 a % drainage 25.6 a 25.7 a 25.7 a 29.7 a 34.9 a 29.8 a Table 4. Data for yield and quality in green-pepper cultivation. A 1 B 1 C 1 D 1 A 2 B 2 First-quality yield kg.m a 5.88 a 5.40 a 3.73 b 3.13 a 3.56 a Commercial yield kg.m a 7.00 a 6.73 a 5.23 b 4.38 b 4.90 a Mean weight g 235 a 247 a 227 a 213 a 252 a 258 a 546

5 Figures mmol l -1 9,00 6,00 3,00 0,00 Evolution of K + in drainage. Year 1. apr may jun jul aug A B C D Fig. 1. Evolution of potassium values in the drainage solutions. mmol l -1 Evolution of K + in drainage. Year 2. 9,00 6,00 3,00 A B 0,00 May Jun Jul Fig. 2. Evolution of potassium values in the drainage solutions. 547