This paper reports about several factorial tests carried out in 1960 and with N P K fertilization for wheat on Ortho Dark Red Latosol in the south of the state of São Paulo, occupied with field vegetation. The results showed that these soils with over 0.10%of total nitrogen did not react to nitrogenated fertilizers, whereas 0.10 e.mg of potassium was the limit of soil reaction. Phosphorus was the element reacting the most showing an evident correlation between response to fertilization and soluble content of the element in the soil. For soils with amounts equal to 0.18 e.mg. of PO4-³ soluble in H2SO4 0.05 N, productions of around 1000 kg per hectare of wheat seeds were reached without any addition of posphorous fertilizers. At this level, any addition of P2O5 implies to an increase of yield. The results indicate further that the fertility indexes established by Catani and others, for the soils of the state of São Paulo do not apply to the Ortho Dark Red Latosol when grown with wheat, concerning the elements nitrogen and potassium.