ISHS Acta Horticulturae 697: International Symposium on Soilless Culture and Hydroponics
RECIRCULATING NUTRITIVE SOLUTION IN SOILLESS CULTURE OF ROSE USING SALINE ALKALINE WATER |
| Authors: | V. Raya, M.A. Díaz, P. Mansito, A.R. Socorro, M.C. Cid |
| Keywords: | recirculation, water saving, nutrient saving, rose quality, irrigation management. |
| Abstract:
Soilless culture of roses has grown rapidly in the Canary Islands. Despite poor water quality (average pH >8.5, electrical conductivity [EC] >0.8 dS/m and NaCl content usually above 5 me/L), reuse of drainage water is a necessity in the Canaries, not only in terms of environmental protection but because water is an extremely limited resource. With the aim of establishing guidelines for recirculation management using low quality water, an experiment was set up to study its effects on productivity of rose cv. Jaguar, cultivated in a greenhouse on tuff-filled (basaltic lapilli) beds, with an open-system control and two recirculating treatments (R1 and R2). The recirculating solutions in R1 and R2 were renewed when drainage EC reached 3.5 dS/m. Irrigation management was similar for the control and R1 treatments, with 10 daily irrigations at fixed intervals; R2 received radiation-dependent irrigations every 200 Wh•m-2. In spite of non-significant differences in flower number, length, weight, or vase life among treatments, recirculation did tend to produce shorter stems therefore reducing first-quality flowers by between 6 and 15%. With the exception of ammonium, all ions accumulated in the recirculating nutritive solution. The concentrations were highest for ions already present in the irrigation water, like magnesium, sodium and chloride, which showed a threefold increase; sulphate, incorporated with ammonium in each irrigation, also accumulated more than the macronutrients potassium, calcium, nitrate and phosphate. Saline accumulation was slower in R2, designed to receive more frequent irrigations on sunny days than R1. Although the solution had to be renewed every 3 weeks for R1 and every 4 for R2, drainage recycling saved water (22% for R1 and 29% for R2) and nutrients (51% and 55% for N, 37% and 44% for P, and 59% and 62% for K, for R1 and R2 treatments respectively). Compared to the open-system control, recycling notably reduced the pollution by leachate run-off; the savings reached 78% and 89% for N, 55% and 75% for P, and 86% and 93% for K, for R1 and R2 respectively. | |
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