. Nitrogen fertilization as top dressing for the corn following black oats under a no-tillage system

Abstract

A field experiment was carried out on a red dystrophic loam oxisol from Tibagi, Paraná State, Brazil, to assessing whether surface-applied urea affects corn development and yield as a result of N-NH₃ losses by volatilization, and whether the partial or full replacement of urea by ammonium sulfate increases the effectiveness of nitrogen fertilization as sidedressing, without incorporation. A randomized complete block design was used, with three replications, in a split-plot experiment. The plots received four rates of N applied as top dressing: 30, 60, 90 and 120kg ha^-1. The subplots were constituted by four application forms: surface-applied urea, incorporated urea, surface-applied ammonium sulfate and surface-applied urea + ammonium sulfate. The N rates led to a linear increase in corn yield, number of grains per ear, ear weight per plant, grain weight per ear, and weight of 1000 grains. Urea, surface-applied or incorporated, and surface-applied ammonium sulfate performed similarly in nutrition and corn grain yield.