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Resposta de híbridos de milho cultivados em diferentes épocas à popula??o de plantas e ao despendoamento

DOI: 10.1590/S0103-84782006000500004

Keywords: zea mays, cultivar, sowing density, tassel.

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Abstract:

current maize hybrids are more tolerant to the increasing of plant population than the hybrids used in the past. it is possible that modern hybrid's better adaptation to crowding is related to the lower apical dominance of the tassel over the ear. this experiment was aimed at evaluating the evolution on maize hybrids commercially released in different times the increase in plant population and at detecting if this progress is related to the reduction of apical dominance. the experiment was carried out in lages, sc, during the 1999/2000 and 2000/2001 growing seasons. a split-split plot design was used. three plant populations were tested in the main plots: 50,000, 75,000 and 100,000pl ha-1. four hybrids commercially released in the 60's, 70's, 80's and 90's, respectively, were assessed in the split plots. each hybrid was analyzed with preserved tassels and with tassel removed at booting in the split-split plot. the trials were installed in 10/30/1999 and 11/02/2000. grain yield was assessed using the variance and regression analyzes. the hybrid commercially released in the 90's (ag 9012) was more demanding in plant population to maximize grain yield when the conditions were favorable to yields higher than 10,000kg ha-1 (1999/2000). at this scenario, tassel interference on ear development was small. on the other hand, grain yield of all tested hybrids was increased by tassel removal under a lower yield plateau (2000/2001).there was no association between higher tolerance to crowding and greater response to detasseling, indicating that the tested hybrid higher endurance to dense stands was not related to the reduction in apical dominance of the tassel over the ear.

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