The objective of this study was to evaluate, under field conditions, in Colina-SP, Brazil, the response of two corn cultivars to six soil compaction levels of an Oxisol regarding the root system development, and to characterize soil compaction by the least limiting water range (LLWR). The experiment was arranged in a randomized complete block design, with strip plots and four replications. The corn hybrids DKB 390 and DAS 2B710 were used. After corn sowing, undisturbed soil samples were collected to determine physical properties and LLWR. At the tasseling stage of the corn plants, three soil samples per plot were taken from the crop inter-row, from the layers 0-10, 10-20 and 20-30 cm, to measure mean root diameter, length density and dry mass. The LLWR was equal to zero when soil density reached the critical level of 1.46 t m-3, corresponding to 92 % of the maximum soil density. Greater soil compaction resulted in greater root dry mass, length density, and diameter. In the 0-10 cm layer an increase in root dry mass and density was possible up to a penetration resistance of 1.23 MPa and 1.43 MPa, respectively. Root dry mass, density and diameter were negatively correlated with the yield of irrigated corn, and therefore represent good soil compaction indicators.
resistance to penetration; water content; root system; Zea mays
