Nitrogen as top-dressing and sowing densities on agronomic characteristics of maize crop

ABSTRACT The main objective of this study was to evaluate the agronomic characteristics of commercial maize hybrids with modern and old architecture, under the influence of nitrogen (N) as top dressing with different plant populations. Two independent experiments were conducted, one in the municipality of Guarapuava (reduced spacing = 0.45 m) and the other in the municipality of Laranjeiras do Sul (conventional spacing = 0.90 m), in the Paraná state, Brazil, in the 2012/2013 growing seasons. The experiments were set in a randomized block design, with three replicates, in a factorial scheme (6 x 3 x 3), corresponding to six maize hybrids (with modern and old architecture), three plant populations (60000, 75000 and 90000 plants ha-1) and three N doses as top dressing (0, 90 and 180 kg ha-1 of N), both installed in October. N doses as top dressing and sowing density influenced the thousand-grain weight in maize hybrids with modern and old architecture. The increase in sowing density reduced stem diameter in the groups of modern and old architecture in Laranjeiras do Sul. Grain yield was positively influenced by N fertilization, being higher at the N dose of 180 kg ha-1 in Guarapuava and Laranjeiras do Sul.