Abstract

Selected abiotic (electric conductivity, pH, oxygen content, chemical oxygen demand, dissolved organic carbon) and biotic (general bacterial and fungal microfloral fluorescent pseudomonads, filamentous actinomycetes, Fusarium oxysporum, Pythium aphanidermatum, biochemical oxygen demand, enzyme activities) factors have been monitored in two distinct commercial hydroponic systems with tomato and ornamental plants with integrated slow filters in supernatant, filter skin and effluent in two successive years. In six small scale experimental systems with two slow filters each (nutrient film technique, crop: tomato) the same parameters were followed to establish possible correlations with filter efficacy against Fusarium oxysporum f. sp. cyclaminis. In half of the systems, the filter skin was enriched with fungal cell wall preparation. Nutrient solutions of the systems showed biggest differences concerning the chemical oxygen demand (COD) (commercial tomato system >> experimental system > commercial ornamental system) and dissolved organic carbon content (DOC). Both factors were positively correlated in supernatant and effluent (e.g. supernatant: r(2)=0.813; p<0.001). A significant reduction of COD and DOC due to filtration was visible only in the commercial tomato system. The biological oxygen demand of the nutrient solutions was always very low (<2 Mg O-2 l(-1)). Absolute oxygen content was always reduced by filtration processes. Electric conductivity and PH of nutrient solution remained unaffected by filtration processes. No significant differences between the growing systems concerning biotic factors have been observed in supernatant and filter skin. Pythiurn aphanidermatum and Fusariurn oxysporum were regularly found in the supernatants and colonized the observed filter skins. All effluents of the systems were free of P. aphanidermatum. Fusarium oxysporum was detected continuously in the effluents of the experimental system while effluents of commercial systems contained only F. oxysporum at one incident. Values for chitinase, cellulase, glucanase and protease enzyme activities of the filter skin were not influenced neither by growing systems nor time. Only xylanase activity showed seasonal influences and activities increased over time (mU = 0.088 (mU week(-1)) * t (week); r(2)=0.546; p<0.001). Filter efficacies against Fusarium oxysporum f. sp. cyclaminis in the experimental systems varied between 98.3%+/- 1.0 (treated) and 979%+/- 1.8 (untreated) but no significant differences could be stated

Published in

European Journal of Horticultural Science
2007, Volume: 72, number: 3, pages: 104-112
Publisher: EUGEN ULMER GMBH CO

SLU Authors

• Bergstrand, Karl-Johan

  • Horticulture, Swedish University of Agricultural Sciences
    

• Alsanius, Beatrix

  • Horticulture, Swedish University of Agricultural Sciences
    

UKÄ Subject classification

Horticulture
Food Science
Fish and Aquacultural Science


Permanent link to this page (URI)

https://res.slu.se/id/publ/16584