1. Dep. of Soil Sciences, College of Agriculture; Univ. of Technology; Isfahan Iran 84154
2. Dep. of Soil Sciences; College of Agriculture, Univ. of Shiraz; Iran
3. Dep. of Environmental Sciences, Section of Soil Quality; Wageningen Univ.; P.O. Box 8005 6700 EC Wageningen The Netherlands
4. Dep. of Environmental Sciences; Univ. of California; Riverside 92521 CA USA