Abstract Water deficit stress is the abiotic factor with the highest impact on crop yield. The objective of this study was to evaluate grain yield (GY), the anthesis-silking interval (ASI) and drought tolerance indices in maize hybrids. We evaluated GY and the ASI of 86 hybrids under two moisture levels (normal irrigation and water stress) for three consecutive years. The stress susceptibility index, water stress tolerance, drought resistance coefficient, drought resistance index, stress tolerance index and harmonic mean were evaluated. There were significant hybrid x environment interactions for GY and the ASI. Differences in the ASI among environments ranged from 0 to 5 days. The hybrids P3862, 1I873, 1I923, 1I862 and 1J1211 showed high GY, associated with the highest drought tolerance indices. The stress tolerance index and harmonic mean indices can be used to identify higher-yielding maize hybrids in environments with and without water restriction.

The objective of this experiment was to characterize the dry matter production of vegetative components (stalk, leaf, husk, and cob) and reproductive components (grain) of the corn plant according to planting time and the grain maturity stage. Eight corn hybrids with different agronomic characteristics were used to carry out the experiments. Two experiments were performed with planting undertaken on 11/11/2007 and 12/12/2007 under a conventional tillage system. The eight corn cultivars were harvested at three grain maturity stages, half milk line, three quarters milk line and black layer. An 8 × 3 factorial (eight hybrids and the three cutting times) randomized blocks design was used, with three replications. Individual analysis of variance was performed for each experiment. Then joint analysis of variance was performed involving the two planting times. The means were grouped and the hybrids used as replications to characterize the components. Delay in planting significantly reduced the dry matter productivity of the whole plant; however, it did not reduce its degradability. The greatest dry matter productivity obtained was that of grain, followed by stalk, leaf, husk and cob. The vegetative components, leaves and husk, lose quality with delay in planting. The leaf is the vegetative component of highest quality, while the cob is the worst. Delay in planting increases the neutral detergent fiber content of the stalk, husk and cob.