Wezel A, Steinmu ¨ller N, Friedrichsen R (2002) Slope position effects on soil fertility and crop
productivity and implications for soil conservation in upland northwest Vietnam. Agric
Ecosyst Environ 91:113–126
Wilford J, Minty B (2007) The use of airborne gamma-ray imagery for mapping soils and
understanding landscape processes. Dev Soil Sci 31:207–220
Wischmeier WH, Smith DD (1978) Predicting rainfall erosion losses – a guide to conservation
planning. Agriculture Handbook No. 537, U.S. Department of Agriculture, Washington, DC
Zhu AX, Hudson B, Burt J, Lubich K, Simonson D (2001) Soil mapping using GIS, expert
knowledge, and fuzzy logic. Sci Soc Am J 65:1463–1472
2 Beyond the Horizons: Challenges and Prospects for Soil Science and Soil. . .
107
productivity and implications for soil conservation in upland northwest Vietnam. Agric
Ecosyst Environ 91:113–126
Wilford J, Minty B (2007) The use of airborne gamma-ray imagery for mapping soils and
understanding landscape processes. Dev Soil Sci 31:207–220
Wischmeier WH, Smith DD (1978) Predicting rainfall erosion losses – a guide to conservation
planning. Agriculture Handbook No. 537, U.S. Department of Agriculture, Washington, DC
Zhu AX, Hudson B, Burt J, Lubich K, Simonson D (2001) Soil mapping using GIS, expert
knowledge, and fuzzy logic. Sci Soc Am J 65:1463–1472
2 Beyond the Horizons: Challenges and Prospects for Soil Science and Soil. . .
107
