Intensive agricultural practices are thought to cause soil structure deterioration. The work reported herein aims to study and analyze the long-term effects exerted by high application rates of N,P,K fertilizer on soil structure as characterized by tensile strength, stability to water, friability, and bulk density of its structural units. No differences were found in the organic matter content between the control and the fertilized plots. Bulk density increased with diminishing the aggregates' diameter and this was attributed to shrinkage and not to differential effects brought about by different N,P,K amounts. In the dry state the structure was more friable and “smaller grained” under high P and without N fertilizers. Water stability was not affected by the differential N,P.K treatments when compared with the control.