Aspectos fitotécnicos e nutricionais do milho doce em função de doses e épocas de aplicação de nitrogênio em cobertura

Abstract

Coverage application effects of different nitrogen doses associated to two application periods on the development and production of two simple hybrids of sweet corn during three agricultural years are evaluated. Experiments were performed in areas featuring eutrophic red nitosoil, with a clayey texture, in Maringá PR Brazil, during the "summer" harvest of the agricultural years 2009, 2010 and 2011. Experimental design comprised totally randomized blocks with four repetitions. Treatments consisted of combinations between coverage N dose levels (0, 45, 90, 135 and 180 kg ha-1 of N), application periods (phenological stage V4 and V8), sweet corn simple hybrids (Tropical Plus and RB-6324), at a factorial scheme 5 x 2 x 2, with three agricultural years. Total data analysis showed that an increase in N doses generally affected the components of the aerial section, plant height, leaf area index, productivity, number of grains per row, number of grain rows per ear and the productivity of commercial de-strawed ears of the sweet corn hybrids Tropical Plus and RB-6324. N coverage application in the N dose 110.84 kg ha-1 provided maximum productivity of commercial ears of 1041 Mg ha-1, regardless of the N application period, hybrids and agricultural years. Moreover, maximum economical efficiency under current conditions was obtained with N dose 102.5 kg ha-1. In fact, N doses 45 and 90 kg ha-1 provided the best economical assets of R$ 1973,1 ha-1 and R$ 863,2 ha-1, respectively, regardless of the period of N application, hybrids and agricultural years. The sweet corn hybrid RB-6324 was higher than Tropical Plus with regard to the productivity of de-strawed ears and the productivity of commercial ears. Results demonstrated that the characteristics plant height, leaf area index, Total N rate of leaf, number of grains per row, productivity of de-strayed ears and protein contents in sweet corn grains had a positive correlationship with the productivity of commercial ears.