The Corg content was determined by wet oxidation with potassium
dichromate (ISO 14235, 1998) and the Ntot was determined
by the Kjeldahl method (ISO 11261, 1995). The C/N ratio was then
computed based on the concentration of Corg and Ntot. The total
content of organic carbon (Corg), total nitrogen (Ntot) as well as
pH was estimated in air dried samples. The pH was measured
potentiometrically in water (1:1) (ISO 10390, 2005). Dry matter
(DM) was determined after the weight loss by drying wet samples
at 105 C (ISO 11465, 1993).