DURATION OF THE SOWING-FLOWERING SUB-PERIOD, PLANT GROWTH AND PRODUCTIVITY OF MAIZE UNDER CONTRASTING CLIMATIC CONDITIONS

Knowledge of the number of growing degree-days in the sowing-flowering period of the corn plant is important for the crop planning. The objective of the present work was to analyze the behavior of different maize hybrids during the vegetative growth stage, under contrasting climatic conditions, with regard to accumulated growing degreedays requirement at sowing-flowering sub-period, plant growth and grain productivity. Eighteen maize hybrids were evaluated during the growing seasons 2007-2008 (normal rainfall) and 2008-2009 (water deficit) in field experiments at the Federal University of Santa Maria. Number of days and degree-days until tasseling and silking, plant and ear height and grain yield were evaluated under the two contrasting growing environments. Under low rainfall conditions, the accumulated degree-days from sowing to tasseling and silking were about 10% higher than under normal rainfall. Plant and ear height were reduced more than 30% and grain yield decreased above 80%. Water deficit at vegetative growth stage resulted in higher degree-days requirements and decrease in grain yields.