In this fourth paper on phosphorus fertilizers for corn the authors report the results obtained in four experiments located on different sites of the State of São Paulo, in which superphosphate was compared with three ground rock phosphates, the comparison being based on their contents of total P2O5. While one experiment was annual, the others were conducted for two, two and five years. The effect of liming was also studied in two of the experiments. Lime and fertilizers were applied only in the first year. In three of the four trials superphosphate was much superior to hyperphosphate and mainly to Serrote-phosphate (from the Serrote hill, near Juquiá. State of São Paulo); in the other trial the last two types of phosphates gave similar results and were only a little inferior to superphosphate. Florida-phosphate, included in two experiments, was practically equal to byperphosphate. The superiority of superphosphate came chiefly from its greater efficiency in the first year; star-ling from the second year the tendency was for equivalence of the phosphates studied. In the experiment conducted for five years the lime application was ineffective in the first two years, but il increased appreciably the yields in the following years. In another experiment, couduceted for two years in a move acid soil, lime was fairly effective even in the first and very effective in the second year. The addition of lime enhanced the effect of superphosphate, but affected contradictorily those of the natural phosphates.