PHYLLOCRON IN A LOLIUM PERENNE L. SWARD: EFFECT OF DEFOLIATION FREQUENCY AND NITROGEN ADDITION

Abstract

The aim of this study was to test the effect of three defoliation frequencies and three levels of nitrogen fertilization on the dynamics of growth, yield and nutritive value of Lolium perenne L. The trial was conducted from June 21^st to November 7^th, 2008. Mini-swards were established in 125 L containers. The experimental design was a randomized complete block with three replicates, with a factorial arrangement of three frequencies of defoliation (1,5, 2,5 and 3,5 leaves per tiller) and three fertilization levels (0, 25 and 75 kg N ha^-1). Phyllocron, leaf elongation and tiller appearance rates, dry matter yield and nutrient content were evaluated. There was no significant interaction between defoliation frequency and nitrogen fertilization level for any of the variables. There were no significant effects of defoliation frequency or nitrogen fertilization on the phyllochron (rate of leaf appearance) and on the rate of tillering. Nitrogen fertilization increased the leaf elongation rate. Both frequent defoliation and N deficiencies resulted in smaller plants. The dry matter yield was higher in pastures defoliated at 2,5 and 3,5 leaves tiller^-1 and those fertilized with high nitrogen levels (75 kg N ha^-1).