For the recommendation domain 1 (RD1), characterized by high initial content for P in the soil and a low level of organic matter (OM), optimal economic rates were 184 kg N/ha and no P application. For the RD2, low P and high level of MO, the optimal rates were 72 kg N/ha and 51 kg P2O5/ha. For the DRl the profitability of fertilizer application was found to be significantly superior to that found in RD2. For fertilization to be profitable in the RD1 the minimum rate of return acceptable to farmers must be inferior to 42%, while in RD2 this rate must be inferior to 93%.