Estabelecimento de pastagens de tifton 85 sob doses de adubação nitrogenada

Abstract

This work was carried out in order to obtain subsidies under the definition of strategies for nitrogen fertilization of pastures of tifton 85, based on monitoring the dynamics changes in the structure of swards. The underlying assumption was that the application of increasing levels of N is a powerful tool for that purpose. The experiment was developed over a Planosol of occurrence in the experimental field of the Universidade Federal Rural Rio de Janeiro, city of Seropédica, Brazil, during the establishment of the pasture, between the months of October, 2006 to January 2007. Treatments consisted of four levels of N (0, 50, 100 and 150 kg N-urea. ha-1), in single application, in plots of 4 x 4 m, arranged in blocks fully randomized, with four repetitions. Together with nitrogen fertilization, the plots received 80 kg P.ha-1 and 150 kg K.ha-1, and Ca as calcareo (1.0 tn.ha-1). The variables were: frequency of occurrence of plants; height of the canopy, leaf growth and leaf area index (LAI), the interception of photosynthetically active radiation (PAR) and the production and partition of dry matter. The results showed that the frequency of occurrence, height and interception of PAR varied according to a standard logistic, whose parameters have been modified to a greater or lesser degree, by the levels of N added. Similarly, at the 87 days after planting, the LAI and the total dry matter produced, but not its partition between leaves and stems, responded to changes in N mineral available in the soil. It was concluded that the application of increasing levels of Nurea, during the establishment of grass tifton 85 was an efficient experimental strategy for the induction of quantitative changes during the development time of swards structure.