@ARTICLE {TITTONELL:2013, title = {Soil heterogeneity and soil fertility gradients in smallholder agricultural systems of the East African highlands}, author = {Tittonell, P. and Muriuki, A. * and Klapwijk, C. J. and Shepherd, K. and Coe, R. and Vanlauwe, B. }, journal = {Soil Science Society of America Journal}, year = {2013}, month = {February}, volume = {77}, number = {2}, pages = {525--538}, issn = {0361-5995}, doi = {10.2136/sssaj2012.0250}, }