Degradation of Pesticides in Nutrient Solution from Closed Hydroponic Systems

• To protect aquatic systems in the Baltic Sea area, zero eutrophication has been proclaimed as one of the Swedish environmental goals. Closed hydroponic systems are generally used today to meet standards on reduced release of excess nutrient-rich drainage water from horticulture. In recent years, concerns have been expressed about emissions of plant protection products (PPP) from indoor cultivation systems to aquatic environments in the vicinity of commercial greenhouses. Some of the active ingredient in pesticides applied to the crop can end up in the nutrient solution (i) after canopy application, through plant run-off and infiltration through the growing medium or into collecting gutters, or (ii) after direct administration to the nutrient solution. This study monitored the concentrations of three PPP (fenhexamid, FEX; pyrimethanil, PYR; imidacloprid, IMI) on six occasions over 21 days in colonised nutrient solution obtained from a closed cropping system for greenhouse tomatoes and incubated at 20°C in darkness. The experiment with FEX (added at 0.01 times the recommended spray concentration) was conducted as a full-scale experiment with six replicates and examined the dynamics of microbiota associated with the nutrient solu¬tion. Monitoring of PYR and IMI (added at 0.01 and 1 times the recommended spray concentration, respectively) comprised chemical analysis of the compound in single samples on six sampling occasions. The results indicate that all three PPP persisted for 21 days in the microbe-colonised nutrient solution under the experimental conditions used.

Ämnesord

LANTBRUKSVETENSKAPER  -- Lantbruksvetenskap, skogsbruk och fiske -- Trädgårdsvetenskap/hortikultur (hsv//swe)

AGRICULTURAL SCIENCES  -- Agriculture, Forestry and Fisheries -- Horticulture (hsv//eng)

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