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In Brazilian agriculture, maize (Zea mays L.) is prominent because of its magnitude of grain production. However, soil compaction changes negatively the soil physical attributes, limiting the crop growth. This study aimed to evaluate physical attributes of a clayey Oxisol (Rhodic Hapludox) under no-tillage, and the relationships between these attributes with maize yield in the Midwest region of Brazil. Besides this, indicators of soil physical quality when subjected to levels of compaction were determined. A randomized complete block design was applied with five replicates. Treatments were induced levels of compaction: a reference condition that reflects 8 yr of no-tillage (NT); no-tillage with additional compaction by tractor traffic in one (NT-1), two (NT-2), four (NT-4), and six passes (NT-6). There was significant correlation (P < 0.01) between all physical attributes of the studied soil. Maize yield was positively correlated to macroporosity (r = 0.41*), and negatively to penetration resistance (r = -0.42*), geometric mean diameter (r = -0.51*), and mean weighted diameter (r = -0.53*). The index of emergence speed, stem diameter, plant height, grain mass, and grain yield decreased as soil compaction increased. The physical attributes evaluated, especially the resistance to penetration and soil macroporosity, reveal the level of soil compaction and can be used as soil physical quality indicators. [ABSTRACT FROM AUTHOR]

In the search for elevating high current levels of productivity and reduction in production costs of corn seeds in Brazil, new technologies are being incorporated into the production system. The aim of this study was to evaluate the physiological quality of seeds of maize in response to nitrogen fertilization and inoculation with Azospirillum brasiliense and Herbaspirillum seropedicae. Two experiments were installed, and in the first the design adopted was a randomized block, and in the second experiment, the design used was a completely randomized, both with nine treatments (control without N and without inoculation, control without N and with A. brasilense, control without N and with H. seropedicae, 30 kg N ha-1 in sowing, 30 kg N ha-1 in sowing + A. brasilense, 30 kg N ha-1 in sowing + H. seropedicae, 30 kg N ha-1 in sowing + 90 kg N ha-1 in topdressing, 30 kg N ha-1 in sowing + A. brasilense + 90 kg N ha-1 in topdressing; 30 kg N ha-1 in sowing + H. seropedicae + 90 kg N ha-1 in topdressing) and four replications. The variables evaluated were: percentage and first count of germination, dry mass and length of seedling, accelerated aging, cold test and electrical conductivity. The dry mass production are affected by inoculation with diazotrophic bacteria in association with nitrogen fertilization. Inoculation of corn seeds with A. brasilense, H. seropedicae and the use of nitrogen fertilizer promotes increase in productivity of corn seed to the extent of 4.73; 5.17 to 8.90%, respectively. The use of A. brasilense improves the physiological quality of seeds of maize by cold test without soil. [ABSTRACT FROM AUTHOR]