Precision agriculture in oil palm plantations: diagnostic tools for sustainable N and K nutrient supply Bernard Dubos, Victor Baron, Xavier Bonneau, Olivier Dassou, Albert Flori, Reinout Impens, Jean Ollivier and Lénaïc Pardon OCL, 26 (2019) 5 Published online: 19 February 2019 DOI: 10.1051/ocl/2019001