SLOW-RELEASE UREA APPLIED TO SURFACE AND REGULAR UREA INCORPORATED TO SOIL ON MAIZE YIELD

Abstract

Urea applied to the soil surface results in high losses of nitrogen (N) by volatilization of NH₃. The use of polymers covering urea granules is an alternative management to reduce such losses. The experiment was carried out in Entisols (Quartzipsament), with 6% of clay, in the 2007/2008 harvest, in Jataí, Goiás State, Brazil, in order to assess the efficiency of the following management systems: urea incorporated to the soil and polymer coated urea applied to the surface, concerning the agronomic and economic aspects of maize cultivation. It was implemented an experimental design in randomized blocks, with eight replications, totaling 24 plots. The covering nitrogen fertilization was performed in a single application, at the V₅ stage. The urea incorporated to the soil resulted in higher values related to ear length and diameter, number of grains per ear, mass of one hundred grains, and relation between earned revenue and invested capital. The highest grain yield and profitability were obtained with the application of urea incorporated to the soil. For each Real (R$ 1.00) invested in the cultivation, the urea incorporated to the soil produced R$ 1.37 as profit.

KEY-WORDS: Zea mays L.; slow-release fertilizer; nitrogen; polymers; no-tillage system.