[1] Northwest A&F Univ, Coll Nat Resources & Environm, Yangling 712100, Shaanxi, Peoples R China
[2] Minist Agr, Key Lab Plant Nutr & Agrienvironm Northwest China, Yangling 712100, Shaanxi, Peoples R China
[3] Gansu Agr Univ, Coll Resources & Environm Sci, Gansu Prov Key Lab Arid Land Crop Sci, Lanzhou 730070, Peoples R China
[4] Nanjing Univ Informat Sci & Technol, Sch Geog Sci, Nanjing 210044, Peoples R China
[5] Chinese Acad Sci, Inst Soil Sci, State Key Lab Soil & Sustainable Agr, Changshu Natl Agroecosyst Observat & Res Stn, Nanjing 210008, Peoples R China
[6] Univ Gottingen, Dept Soil Sci Temperate Ecosyst, D-37077 Gottingen, Germany