Soil samples were analysed for pH (1 :2.5, w/v), electrical conductivity (EC, 1 :2, w/v), total OC (Walkley and Black method), TN (Kjeldahl method), available phosphorous (Olsen method), total content of CaC[O.sub.3] (calcimeter
method), active carbonates (ammonium oxalate method), exchangeable bases (Ca, K, Mg and Na; inductively coupled plasma optical emission spectroscopy method) according to methods described in Swift (1996).
To calculate the carbonate mass content of each sample, the carbonate content was determined by measuring its rate of response to dilute hydrochloric acid using a Dietrich-Fruhling Calcimeter
. Its carbonate mass content was then defined by Equation 3:
Soil particle size distribution (texture) was determined with a hydrometer (Bouyoucus, 1962), calcareous content with a Scheibler calcimeter
(Allison and Moodie, 1965), organic carbon content with Walkley-Black method (Nelson and Sommers, 1982), soil reaction (pH) with a pH-meter in a 1: 2.5 soil/water suspension (Horneck et al., 1989), electrical conductivity (EC) with a conductivity-meter in a soil extraction (1: 5 soil/water) (Horneck et al., 1989), and BD with Black (1965) methodology.
These soil samples were analyzed (Table 1) for pHs (Jenco pH meter 6718, Taipei Hsien, Taiwan, R.O.C.), electrical conductivity (ECe) by a conductivity meter (HI 8033, Hanna Instruments, Woonsocket, USA), particle size distribution by the hydrometer method (Bouyoucos 1962), organic carbon by the Walkley-Black wet combustion method (Nelson, Sommers 1982), and lime (CaC[O.sub.3]) by the calcimeter
method (Moodie et al.
Calcium carbonate content was determined using a calcimeter
. The soil organic matter was measured according to Nelson and Sommers (1996).
Total CaC[O.sub.3]% is determined by volumetric method of the "Bernard Calcimeter
," while active CaC[O.sub.3]% is determined by contact with a specific extraction reagent, "ammonium oxalate," at 0.2 N.
(xix) Active lime (ammonium oxalate method, calculated by means of a gasometric dosage of the C[O.sub.2] of the ammonium carbonate, formed by reacting the calcium carbonate of the sample with a solution of ammonium oxalate with the aid of a Bernard calcimeter
CaC[O.sub.3] was determined by using calcimeter
method as mentioned by Allison and Moodie .
Total carbon and inorganic carbon was determined by the Iowa State University Plant and Soil Analysis Lab, Ames, IA, USA, using the dry combustion and modified pressure calcimeter
Inorganic C as CaC[O.sub.3] was determined using a Scheibler calcimeter
; pH was measured in 0.01 M Ca[Cl.sub.2] using a glass electrode (soil : solution ratio 1 : 2.5).
If soil pH was greater than 7.1, inorganic carbon concentration was determined using a modified pressure calcimeter
method (Sherrod et al.