ISHS Acta Horticulturae 644: International Symposium on Growing Media and Hydroponics
DISINFECTION OF NUTRIENT SOLUTION IN CLOSED SOILLESS SYSTEMS IN ITALY |
| Authors: | A. Garibaldi, A. Minuto, D. Salvi |
| Keywords: | hydroponics, disinfection, gerbera, Phytophthora cryptogea, sodium dichloroisocianurate, metalaxyl |
| Abstract:
In 1999, several active and passive methods of disinfection of nutrient solutions in closed soilless systems were evaluated in order to find the technique most easily transferable to Italian growers. The experiment was carried out by testing the effect against root rot on gerbera plants caused by Phytophthora cryptogea. Gerbera plants (75 days old) were transplanted on 10/06/99 in plastic pots (5 L) in the growing steamed media (80% v/v pumice 20% v/v peat). Pots were kept on concrete benches and provided each one of water irrigation system. On 11/08/00, two plants in each row were inoculated with one isolate of Phytophthora cryptogea. On 01/10 and 02/01 the previously inoculated plants, completely wilted, were replaced with new plants immediately inoculated with the pathogen. The number of infected plants contaminated through nutrient solution was counted. The best control of root rot was obtained with the application of metalaxyl (20 ppm), followed by sand filtration and UV radiation. A strong reduction in the yield, expressed as number of flowers m-2 and number of flowers harvested from healthy plants grown in recycled water treated with 50 ppm of sodium dichloroisocianurate was observed. Moreover, in the presence of such treatment, a strong reduction of stem length was observed. Such phytotoxic effect was still present even when the dosage of dichloroisocianurate was reduced. Metalaxyl provided interesting results, being less phytotoxic: however, its usage is complicated by the presence of its residues in drained and stored water. The sand filtration system used, even completely different from the slow sand filtration method described by Wohanka (1995), gave interesting results. UV radiation strongly reduced the spread of P. cryptogea too, but its efficacy was maintained only with constant cleaning of UV lamp. | |
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