this soil is a silty clay (Stagnic Anthrosol).
Stones and obvious pieces of organic materials were removed. After that, samples were stored in plastic
bags in a refrigerator at 4 °C for further experiments. Some physico-chemical characteristics of the soil
are shown in Table 1. Soil organic C content was determined by the Walkley and Black dichromate
oxidation method [18]. Soil pH was measured in a 1:2.5 soil-water slurry using a glass electrode.
Saturation paste extracts were prepared, the electrical conductivity (EC) was measured and the K+
and
Na+
concentrations were analysed by a PE-Zeemam-5100 atomic absorption spectrophotometry (AAS).
Soil total nitrogen (TN) was estimated using the semi-micro Kjeldahl method. Available phosphorus was
determined by the classical Olsen method [19]. Exchangeable cations were extracted with 1.0 mol/L
ammonium acetate (1:4 w:v for 2 h in a rotary shaker) and Ca2+, Mg2+, K+
and Na+
in extracts were
analyzed by AAS. Clay mineral compositions were identified by X ray diffraction analysis.