It is well accepted today that many fertilizers are acid forming while others are basic forming materials. Pertinent data on this subject, obtained in fertilizers experiments with corn, are reported in this paper. Two experiments are being carried out. One is located in the "terra roxa misturada" type of soil, while the other is in the "massapé" soil. Ammonium sulfate, superphosphate, and potassium chloride have been applied continuously to the same plots in these experiments for 16 and 12 years, respectively. Composite soil samples were taken from 3 replicates of each of the following treatments : check, N, P, K, NPK, (2N)PK, N(2P)K, and NP(2K). In the treated plots separate samples were taken in the rows and in between the rows. A comparison of the results from chemical analysis of the soil samples showed that ammonium sulfate increased soil acidity while superphosphate and potassium chloride did not. An increase of exchangeable potassium was noticed in the plots receiving potassium chloride, and an increase of phosphorus soluble in 0.05 normal sulfuric acid or in the mixture of 0.025 normal ammonium fluoride plus 0.05 normal sulfuric acid was noticed in the plots receiving superphosphate.