ISHS Acta Horticulturae 614: VI International Symposium on Protected Cultivation in Mild Winter Climate: Product and Process Innovation
RECIRCULATING NUTRITIVE SOLUTIONS IN SOILLESS CULTURE WITH LOW TECHNOLOGY - THE "RIVIERA" SYSTEM |
| Authors: | E. Farina, C. Allera, L. Volpi, C. Dalla Guda, T. Paterniani, M. Palagi |
| Keywords: | Water budget, nutrient budget, environmental-friendly cultivation, rose cultivation |
| Abstract:
A research aimed at defining a method for recirculating nutritive solutions in soilless culture with low technology was begun in 1996. A variant of a substrate cultivation with closed loop system was tested with recovery of drainage in a tank by gravity and daily refilling by fresh solution up to the maintenance of limit values of E.C. and pH. The exhausted solution (E.C. and pH over the limit values) was stored in a separate tank and fresh nutrient solution was supplied for recirculation. After U.V. treatment for disinfection, a chemical analysis of the exhausted solutions was performed and then N, P, K, Ca, Mg, levels were adjusted to set-point values. The regenerated nutritive solution was reused. The nutrient solution was distributed by pipes provided with sprinklers and laid on the substrate surface near the container wall and enclosed into a chamber created by a polypropylene sheet. The system was tested by a series of experiments on roses grown for cut flower production in pumice. In the first experiment, softened water (exchange of Ca and Mg by Na) and limit values of 4.0 mS/cm for E.C. and 5 for pH were utilized. An 18 months recycling was possible. Recycling was prolonged for a 6 month period but some problems arose from the regeneration of the nutritive solution with high E.C. and Na levels. In the second experiment, tap water containing Ca and Mg was used. The limit values for recirculating nutritive solution was fixed at 3.0 mS/cm (E.C.) and 5 (pH). The nutrient solution was recirculated for 12 months without any problem. Water consumption was 0.28 and 0.41 L/day/plant, nutrient consumption was 90% and 80%, flower yield was 13.1 and 14.0 commercial grade flowers/plant in the first and in the second experiment respectively. The water consumption and the E.C. of the nutritive solution were monitored in three subsequent short-term experiments carried out with or without mulching (presence of the sprinkler chamber above the substrate). The presence of mulching determined an important decrease in water consumption and in E.C. rise facilitating the long-term recycling. On the whole, the system proved suitable to produce good quality flowers with sufficient yield and demonstrated its reliability. Recycling was possible up to a period of 18 months. In practice, the regeneration of the exhausted solution can be done when its economic value is equivalent to the cost of the chemical analysis. | |
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