1. Key Lab. of Plant-Soil Interactions, Key Lab. of Plant Nutrition, Dep. of Plant Nutrition; China Agricultural Univ.; Beijing 100094 PR China
2. Dep. of Soil Quality; Wageningen Univ.; PO Box 47 6700 AA Wageningen The Netherlands
3. Dep. Soil Physics, Ecohydrology, and Groundwater Management; Wageningen Univ.; PO Box 47 6700 AA Wageningen The Netherlands