Sowing time of popcorn during the summer harvest under supplemental irrigation in Ferralic Nitisol and subtropical climate

The aim of this study was to investigate the effect of sowing time on the phenotypic response of popcorn grown during the summer harvest (first season), with supplemental irrigation. Experiments were performed in the 2009/2010 and 2010/2011 agricultural years in a Ferralic Nitisol, in the northwestern region of Parana State, Brazil, using a randomized complete block design with four replications. Treatments consisted of combinations of five sowing times and two commercial popcorn hybrids (IAC-112 and IAC125) in a 5 x 2 factorial scheme. The evaluated phenotypic characteristics were as follows: plant height, leaf area index, ears per plant, thousand-grain weight, grain yield and popping expansion. The obtained data were subjected to individual variance analyses for each agricultural year. A delay in sowing time limited both the growth and vegetative development of plants, although the first sowing time of each agricultural year (Oct. 6 th 2009 and Oct. 4 th 2010) resulted in better phenotypic characteristics of the popcorn crop. Temperature was the environmental factor with the strongest influence on the phenology, growth and vegetative development of popcorn plants. Grain yield decreased 1.1% (46.8 kg ha -1 day -1 ) for the first sowing time in 2009/2010 and 1.2% (53.2 kg ha -1 day 1 ) for the first sowing time in 2010/2011. The IAC-125 hybrid surpassed the IAC-112 and produced the best results for most of the