Eine modifizierte Methode zur Erfassung der Dehydrogenaseaktivitaet (TTC-Reduktion) im Boden nach Herbizidanwendung.
1993
Malkomes H. P.
A comparison of results from different dehydrogenase activity (TTC-reduction) investigations may be difficult, because many methodological modifications are used. These investigations, therefore, should contribute to standardization. Three agricultural soils were treated with a single and 10 times concentration of four herbicides, which results from a simulated penetration of the field dosage in 5 cm depth. For eight weeks soil was sampled and dehydrogenase activity was measured spectrophotometrically after extraction of formazan by aceton + centrifugation using several modifications (incubation period: 2 hrs + glucose; 4 or 24 hrs + glucose; wavelength: 485 nm; 546 nm). Short incubation periods always showed low activity levels, but in all cases extinction values were higher at 485 nm than at 546 nm. But nevertheless, the specific activity levels of the soils could be observed by all modifications. The same applies to most of the herbicide effects, 'Fluessig Herbogil' (dinoterb) as well as the higher concentrations of 'Ustinex KR' (amitrole + MCPA + methabenzthiazuron) and 'Lentagran' (pyridate) in soil caused stronger inhibitions (over 40%), whereas 'Harmony' (thifensulfuron) was only slightly effective. Depending on their low extinction values short-term incubation seems to be less suitable for ecotoxicological evaluation in inactive soils. In this particular soil the greatest differences occurred after the different measurements. For further tests an incubation for 24 hrs without glucose and a measurement at 546 nm is recommended as a standard, whereas the other variations may be used only for special purposes.
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