The calcium carbonate equivalent (CCE) content was determined by analyzing the evolution of CO2, after reaction with dilute hydrochloric acid, in a Bernard calci — meter (MAPA 1986). The total organic carbon content was determined by dichro­mate oxidation of the samples and subsequent titration with ferrous ammonium sulfate (Yeomans and Bremner 1989). The total Kjeldahl N was determined by semimicro-Kjeldahl digestion (Bremner and Mulvaney 1982). The total concentra­tions of P, K, Ca, Mg, Na, Fe, Mn, Cu, Zn, Cd, Ni, Pb, and B were analyzed by inductively coupled plasma mass spectrometry after digestion of samples in con­centrated aqua regia (McGrath and Cunliffe 1985).

5.2.3 Statistical Analysis

Statistical analyses were carried out using the Statistical Package for Social Science (SPSS® Windows version 13.0) and Excel Statistics 2003 for Windows.