@ARTICLE {PYPERS:2006, title = {Plant-available P for maize and cowpea in P-deficient soils from the Nigerian northern Guinea Savanna: comparison of E- and L-values}, author = {Pypers, P. and Van Loon, L. and Diels, J. and Abaidoo, R. and Smolders, E. and Merckx, R. }, journal = {Plant and Soil}, year = {2006}, volume = {283}, number = {1-2}, pages = {251--264}, }