the objective was to evaluate the application of phosphorus doses in parcels in the cotton crop in the systems of cultivation under irrigation and rainfed, being aimed the higher efficiency of phosphate fertilization, in comparison to the traditional application, only at sowing. the experiment was carried out in quartzanic neossoil, in the north region of minas gerais. the adopted design was randomized blocks, with three replicates. the treatments were the doses of 50 and 120 kg ha-1 of p2o5 applied in four ways: ps, p1, p2 and p3 [100/0; 75/25; 50/50; 25/75% of the dose of phosphate fertilizer applied, respectively at the sowing and at 35 days after the emergence (dae)], in the irrigated and rainfed crops. two additional treatments, without p, in the crop without and with irrigation, completed the eighteen studied treatments. the increase of the p doses increased the dry mass of aerial part and the number of reproductive structures at 80 dae, the relative efficiency of the phosphate fertilization and the productivity of cotton in bull. the response to p doses occurred only under irrigation. the parceled application of the phosphate fertilizer did not increase the efficiency of the fertilization in the cotton farm in quartzanic neossoil.