PHYLLOCHRON, HERBAGE MASS AND NUTRITIVE VALUE OF A Lolium perenne L./Trifolium repens L. PASTURE SUBJECTED TO THREE FREQUENCIES AND INTENSITIES OF DEFOLIATION

Abstract

The aim of this study was to determine the effect of three frequencies and three intensities of defoliation and their interaction on (a) herbage mass, (b) nutritive value, (c) species composition of the pasture, (d) phyllochron (rate of leaf emergence) of Lolium perenne L. and (e) thermal sum required to produce one leaf.
The study was carried out from May 14 to November 30, 2007. A total of 27 cylindrical plastic containers with a capacity of 125 L were used, in which were installed "mini-swards", obtained from a pasture sown with Lolium perenne and Trifolium repens in its second year of production.
Nine treatments were used, three cutting frequencies based on number of leaves per tiller (1.5 - 2.5 - 3.5 leaves tiller-¹) and three defoliation intensities based on the residual height (2 - 5 - 8 cm).
Treatments defoliated at 2.5 and 3.5 leaves/tiller showed a greater herbage mass production than those defoliated to 1.5 leaves. Defoliating the treatments at a lower residual height (2 cm) resulted in a reduced herbage mass production. Crude and soluble protein content decreased with lower frequency of defoliation, however digestibility (D value) increased. Phyllochron was not significantly changed by defoliation treatments, ranging between 7 to 25 days. The termal sum varied between 21 and 91 degrees to produce one leaf.