Dehydrogenase activity
3 g of soil sub-samples were weighed into a 50 ml polypropylene centrifuge tube and mixed with 4 ml phosphate buffer (pH 7.6 ) and 1 ml 3% 1,3,5-triphenyiltetrazolium chloride (TTC) solution.
The centrifuge tubes were incubated for 24 h at 37°C in the dark.
After incubation, triphenylformazan (TPF) formed by reduction of TTC was extracted with 10 ml acetone. Tubes were shaken in an orbital shaker at 300 rpm for 30 min, centrifuged (2000 rpm, 5 min), and the supernatant was filtered with filter paper (S&S N°859).
Blanks without the addition of TTC were carried out in the same manner.
The concentration of TPF was determined by spectrophotometrical measurements at 485 nm, and the results were expressed as g TPF g-1 soil 24 h-1.