Bado, B.De Vries, M.Haefele, S.Marco, M.Ndiaye, M.2014-11-162014-11-162007Communications in Soil Science and Plant Analysis, 2007; 39(1-2):202-2060010-36241532-2416http://hdl.handle.net/2440/87186Published online: 31 Mar 2008. For Erratum see Communications in Soil Science and Plant Analysis, 2008;39(3-4):626-626Soil‐test correlation and calibration, a useful tool for fertilizer recommendations, has been little used in West Africa. Soils from a long‐term fertility experiment have been used to study the relationship between rice yields and soil extractable phosphorus (P) with Bray 1 and Olsen methods. The Cate and Nelson graphical method was used for critical limits of soil P determination. The critical limits of soil extractable P at 95% relative grain yield were 9 mg P for the Bray 1P and 17 mg P kg−1 for Olsen P. The Olsen P was more correlated (r=0.63) with rice grain yields than Bray P (r=0.50), but a strong correlation (r=0.92) was also observed between the values of the two methods. Results indicate that at levels less than these critical levels of extractable P, P fertilizers should be applied to increase rice yields.enCopyright © Taylor & Francis Group, LLCCritical level; fertilizer; phosphorous; rice; soilJournal article003000732910.1080/001036207017591780002526671000152-s2.0-3894909830775293Haefele, S. [0000-0003-0389-8373]