Recirculating Nutrient Solution in Strawberry A. Peralbo, F. Flores and J. López-Medina Dpto. Ciencias agroforestales. Universidad de Huelva Spain Keywords: Soilless, closed system, cork composted, compost, peat Abstract The nutrient solution in closed systems accumulates toxic ions and increases the EC during the long time of growing, both of these processes are harmful for strawberry, which is very sensitive. Strawberry response to leachate recycling in greenhouses has not been studied yet in Spain. The objectives of this work was to examine the effect of recirculating nutrient solution, determining strawberry response to temporal salinity and specific ion accumulation in recycled greenhouse leachates, it was using two different types of organic substrates like peat and cork composted, also it was tested with the open system in each substrate. The closed system was combined with slow sand filtration for disinfestation of the recirculated nutrient solution. This experiment was carried out from October to May in 2002. Substrates were filled into horizontal throughs as 10 l per m 2. Camarosa plug plants were planted the 5 th of October and the density of plantation was 11 pl/m 2. Cl -, Na + 2- and SO 4 were considerably increased (between 115 and 170 %), concentrations upper 8 mmol of Cl - and Na + were found in - - lixiviates. H 2 PO 4 and NO 3 presented different behaviour between peat and cork. Possibly, cork was not sufficiently composted and the consumption of H 2 PO - - 4 and NO 3 was upper than peat. Cork presented a high alkaline reaction which produced problems with micronutrients, overall Fe, generating clorotic leafs in closed systems. Yield was not affected by recycling. There were not significant differences between open (5,91 and 5,4 kg/m 2 for peat and cork respectively) and closed systems (5,56 and 4,17 kg/m 2 for peat and cork respectively) in respect to total yield. The peat gave the highest yield among the tested substrates in each system. Recirculation is possible and it does not present a great problem for growing strawberry in soilless, however it is necessary adjust multiple factors of this system which will improve the yield. INTRODUCTION Strawberry is a key crop in Huelva (Spain) as it can be deduced from its numbers. The value of strawberry production is more than 340 millions, with an acreage higher than 6.700 ha and a total yield of 300.328 t (www.cap.junta-andalucia.es, 2002). In Huelva, there is a high concentration and specialisation of this crop, which means 86% of the national crop acreage, 91% of national strawberry production, and 94% of national strawberry exports (www.mapya.es, 2002). Considering that strawberry crop is repeated year by year (without rotations) and keeping in mind that grown varieties are extremely sensitive to soil borne phytopathogens, soil disinfestation is indispensable, being Methyl Bromide (MB) the most widely used product. Nevertheless, the established association between MetBr and its ability to degrade the ozone layer has determined its urgent elimination before 1/1/2005, except for critical uses. Banning MB has acted as a catalyst for the ongoing development of new and modified technologies such soilless growing systems. Pathological and environmental problems have led to increased interest in soilless culture and have raised the necessity of recycling the major resources in modern agricultural systems. In Spain has been prepared an inventory of materials suitable for use as growing media for ornamental potted plant production (Abad et al., 2001). For avoiding pollution of the ground and surface water with fertilisers, the leaching are reused in closed cultivation systems. Peat has been the substrate more used, but there are growing restrictions on its extraction, because the resources of peat are limited and have generated an interest for alternative materials (Raviv et al., 1986), like composts. The aim of this work was to examine the effect of recirculating nutrient solution, determining Proc. IS on strawberry Soilless Cult. and response Hydroponics to temporal salinity and specific ion accumulation in Ed: M. Urrestarazu Gavilán Acta Hort. 697 ISHS 2005 101
recycled greenhouse leachates, and using two different types of organic substrates like peat and cork composted, it was tested with the open system in each substrate. The closed system was combined with slow sand filtration for disinfestation of the recirculated nutrient solution. MATERIALS AND METHODS Camarosa fresh tray plants were grown under greenhouse in Palos de la Frontera (Huelva) using elevated horizontal troughs filled with peat and cork composted. The plant density was 11 plants/sq m. The date of planting was the 10/5/01. For each 11 plants had 10 liters of substrate. Recycling of the nutrient solution was continued for 8 months. The drain solution was automatically added into the nutrient solution prepared for applying in the closed soilless systems. The nutrient solution was prepared in function of the drain solution in closed soilless system. The drain solution was disinfested using slow sand filtration. Each replication had its own nutrient solution, without mixing nutrient solutions between replications. Chemicals analysis to determine NO 3 -, NH 4 +, HCO 3 -, PO 4 3-, K +, Ca 2+, Mg 2+, SO 4 2-, Na +, Cl -, Fe, B, Mn, Cu, Zn were done to the nutrient solution applied and the drain solution each four weeks. Fruit was harvested twice a week from December to May, and graded into classes. The main experiment was established in a 2 x 2 factorial design with three replications: Systems: Open and Closed soilless with slow sand filtration. Substrate: Peat and composted cork. RESULTS AND DISCUSSION Dynamic of Nutrients The results showed that Cl -, Na + and SO 4 2- were considerably increased, between 115 and 170 % (Fig. 1), concentrations upper 8 mmol of Cl - and Na + were found in lixiviates (Fig. 2), Lieten (2000) considers high levels of Cl -, Na + and SO 4 2- can be a limiting factor for recycling the drainage. PO 4 3-, NO 3 - and micronutrients presented different behaviour between peat and cork (Fig. 1). Possibly, cork was not sufficiently composted and the consumption of PO 4 - and NO 3 - were upper than peat. Cork presented a high alkaline reaction (increasing bicarbonates levels in drainage) which produced problems with micro-nutrients, overall Fe, generating clorotic leafs in closed system. Level of potassium were reduced overall at productive stage. Accumulative ions in drain solution (overall SO 4 2-, Na +, Cl -, Ca 2+, Mg 2+ ) were mainly built up from March, when the development the plants was considerable, due to increase the radiation and the temperature. Peat considerably released more nutrients than composted cork. Irrigation, Consumption and Losses and Savings of Nutrient Solution Plants grown in peat needed more irrigation (Table1). In closed systems plants presented more drainage percentage due to less consumption, it could be related with the salinity conditions in root zone. The 84 % drain solution was recycled, the rest was discharged in closed soilless system. 102
Yield Yield was not affected by recycling. There were not significant differences between open (5,91 and 5,4 kg/m 2 for peat and cork respectively) and closed systems (5,56 and 4,17 kg/m 2 for peat and cork respectively) in respect to total yield. The peat gave the highest yield among the tested substrates in each system. CONCLUSIONS 1. Recirculation is possible and it does not present a serious problem for growing strawberry in soilless, however it is necessary adjust multiple factors of this system which will improve the yield. 2. Composted cork must be well done for supplying micro-nutrients in perfect conditions to plant. ACKNOWLEDGEMENTS This work was supported by national project Closed soilless growing system: a sustainable solution for strawberry crop in Huelva (Spain) (AGL2000-1296-C02-01). Famidan, S.L. Yara S.A. Literature Cited Abad, M., Noguera, P. and Burés, S. 2001. National inventory of organic wastes for use as growing media for ornamental potted plant production: case study in Spain. Bioresource Technology. 77:197-200. Lieten, F. 2000. Recyclage de la solution nutritive dans la culture sur substrat. Le Fruit Belge. 487:170-172. Raviv, M., Chen, Y. and Inbar, Y. 1986. Peat and peat substitutes as growth media for container-grown plants. In: Chen, Y., Avnimelech, Y. (Eds). The role of organic matter in modern agriculture. Martinus Nijhoff publishers, Dordrecht, Holland. 257-287. 103
Tables Table 1. Daily Irrigation, consumption and drainage percentage (average) in different growing systems. System Substrate Irrigation (cc/plant day) Consumption (cc/plant day) Drainage (%) Open Peat 134.4 107.52 20.52 Open Cork 118.6 95.68 19.33 Closed Peat 134.4 102.66 23.61 Closed Cork 118.6 86.86 26.76 Figures 25 % 20 15 10 5 NO3 PO4 SO4 Cl bicarb K Ca Mg NH4 Na B Fe Mn Cu Zn -5-10 Open cork Closed cork Open peat Closed peat Fig. 1. Ions accumulation (percentage) in different systems of culture. 104
25,0 0,70 NO 3 0,60 20,0 NH 4 0,50 15,0 0,40 10,0 0,30 0,20 5,0 0,10 0,0 PO 4 SO 4 3,50 7,00 2,50 1,50 0,50 1 1 Cl 7,00 Ca 1 4,50 Mg 1 Na 3,50 2,50 1,50 0,50 12/18 1/2 1/17 2/1 2/16 3/3 3/18 4/2 4/17 5/2 5/17 2 2 K + 1 1 Fig. 2. Dynamic of macro-nutrients (mmol/l) and micro-nutrients (µmol/l) in applied nutrient solution and drainage of different systems of culture. 105
12 8 10 Mn 7 Cu 6 8 5 6 4 4 3 2 2 1 12 Fe 10 9 B 10 8 8 7 6 6 5 4 4 3 2 2 1 18,0 0 16,0 0 Zn 14,0 0 12,0 0 10,0 0 1/29 2/12 2/26 3/12 3/26 4/9 4/23 5/7 5/21 nutrient solution applied open cork nutrient solution applied closed cork nutrient solution applied open peat nutrient solution applied closed peat Drainage open cork Drainage closed cork Drainage open peat Drainage closed peat Fig. 2. (Continued) Dynamic of macro-nutrients (mmol/l) and micro-nutrients (µmol/l) in applied nutrient solution and drainage of different systems of culture. 106