Comportamiento poblacional de una colección de Urochloa brizantha (Hochst. ex A. Rich.) R.D. Webster en asociación con Stylosanthes guianensis CIAT-184 (Aubl.) Sw.

The objective of this study was to evaluate the structural and floristic composition performance of 19 accessions of Urochloa brizantha, associated with Stylosanthes guianensis CIAT-184 on an acid soil, after three years of simulated grazing. The variables live shoots-dead shoots ratio and floristic composition were analyzed. The measurements were made in all the rotations during the experimental period. The substitution of dead shoots was favorable in most of the treatments; four accessions stood out (CIAT-16322, CIAT-26646, CIAT-16332 and CIAT-16335) in which, at the end of the period, the index of substitution of dead shoots was over two. From the accessions, 36,6% reached a percentage higher than 80% at the end of the experimental period; the accessions CIAT-16317, CIAT-16335 and CIAT-16332 were the ones with higher presence of the base pasture (> 90%). In all the associations the legume was represented in a low percentage (< 16%); while the weeds remained, in most cases, below 20%. In general, the evaluated U. brizantha accessions showed an acceptable persistence or stability in time, and CIAT-16322, CIAT-26646, CIAT-16332 and CIAT-16335 stood out. [ABSTRACT FROM AUTHOR]