Title: Corn yield as a function of amounts of nitrogen applied in bands
Abstract: The aim of the current paper is to study the effect of different amounts of nitrogen applied in bands of corn hybrids on variables related to corn plant growth and its yield components. The experiment was carried out under no-tillage system at Guarapuava, PR, Brazil, throughout the period of October 1st 2009 to March 20th 2010. The treatments resulted in the combination of two simple hybrids of corn (P30R50 and AG8025) and six doses of nitrogen applied in bands (0; 75; 150; 225; 300 and 375 kg N ha-1 in urea form). The treatments were 12 arranged in a 2x6 factorial design of randomized blocks in four replications. The corn hybrid AG8025 had a small number of leaves, smaller rows of grains per stalk and insertion height of primary stalk compared to the hybrid P30R50. However, with a greater plant height, higher overall dry phytomass and productivity point out the influence of genetic variability on the crop. Nitrogen doses influenced significantly biological variables, such as plant height at the phenological stages V9 and R1, insertion height of the primary stalk, branch diameter, number of photosynthetically active leaves at R1, stalk diameter, one thousand grains weight and productivity. 295 kg de N ha-1 dose provided estimated yield of 13,032.93 kg ha-1. Factors, such as hybrids and N doses, did not affect harvest index, whose average value corresponded to 0.52. Yield was positively correlated to most of the variables in the study, outstanding yield components, such as dry phytomass of grains per stalk and overall phytomass of the aerial part per plant. It is concluded that knowing the effect of N on corn plant physiology makes the characterization of yield possible and helps in the selection of corn plant as a parameter for N management in bands. Key words: Zea mays L., yield component, nitrogen, harvest index.