In 1958-59 four experiments were conducted on different soil types of the State of São Paulo, in which ordinary and triple superphosphates were compared in the presence of NK and with the addition, or not, of 25 kilograms of zinc sulfate per hectare. The phosphorus fertilizers were used at the dosage of 80 kilograms of P2O5, per hectare. The greater part of the nitrogen was top-dressed; the remaining fertilizers were side-placed at planting time. The responses to phosphorus reached + 119 and + 97% in two trials, decreasing to +18 and -6% in the others. In three localities the responses to zinc, although small, were positive in the presence of ordinary superphosphate and negative in that of triple superphosphate; in the other place they were respectively + 29 and + 7%. While triple superphosphate was consistently inferior in the presence of zinc, in its absence it was a little superior in three trials, being appreciably inferior only in one trial. As an average of the four experiments the relation between the yields obtained with ordinary and triple superphosphates was 100:90 in the presence and 100:100 in the absence of zinc. It is supposed that the noxious influence of zinc, which could be evidenced only in the presence of triple superphosphate, was reduced by the calcium sulfate contained in ordinary superphosphate. The superiority of the latter in one of the trials, which was observed even in the absence of zinc, is attributed to sulfur deficiency in the experimental area.