We grew Zea mays in treatments with different compaction levels: a light bulk density (LC), 1.30 Mg m^–3; a moderate bulk density (MC), 1.45 Mg m^–3; and a severe bulk density (SC) 1.60 Mg m^–3. Each compaction level had treatments with coarse structure, as found in the field, and with fine structure, after passing the soil through a 2-mm sieve. All treatments had the same initial matric potential. We grew eight maize plants in each container for 28 d. At the end of the experiment, treatments were broken open and roots were counted. Permeability to air decreased and soil strength increased with soil compaction. At every compaction level, the permeability and strength were higher in the coarse- when compared to the fine-structured soil. Root densities decreased with increasing soil compaction especially for MC to SC. The penetration of roots in the most compacted soil was less inhibited in coarse-structured soil. Top growth was highest in MC and considerably lower in SC. In LC and MC, top growth was greater in the fine-structured soil, whereas in SC it was greater in the coarse-structured soil. We found an optimum crop response for the MC treatment when compared to treatments with either more or less compaction.