After destructive sampling, the soil was carefully mixed and samples of 20 g soil were extracted using 80 ml of 0.5 M K2SO4. Other 20-g soil samples were first fumigated with chloroform for 24 h and then extracted in the same manner. The extracts were frozen until their analysis for the total C and N concentration using an Shi-madzu TOC-VCPH analyzer (Vwp, SHIMADZU, Japan) and auto analyzer (AA3, SEAL, Germany), respectively.