Job Kihara presents a research, which tries to understand variability in crop response to fertilizer and amendments in Sub-Saharan Africa (SSA). The objectives of the study are to identify i) soil fertility constraints to crop production, ii) the occurrence of responsive and non-responsive fields, iii) key response patterns, and iv) to identify existing links between crop response to nutrient application and soil spectra. The research set up allows scientists to collect data on more than 400 African farms. The researchers analyse crop responses on eight fertilizer treatments. In most sites, results show that the nutrient limitations are in order N>P>K. In acidic soils, K is as limiting as N and P. Results demonstrate a wide existence of non-responsive soils to NPK treatments compared to soil amendments consisting of lime, manure, and multi-nutrients. In his presentation, Job Kihara only shows a tiny part of the research he is involved in. They create an amazing website containing many information on African soils explored with interactive maps. For further informations, have a look at the website of the African Soil Information Service.