Study of the variation in the structure of the vegetation of two cultivars of Panicum maximum jacq. (guinea grass and tobiata) subjected to different kinds of management. 1. dry matter production tiller and bulk density

Abstract

This work was carried out at the FCAV-UNESP Campus of Jaboticabal, Brazil, to study the effects of N fertilization (0 and 50 kg N/ha/cut), three sucessive periods of growth (from Dec., 21 to Feb. 1; from Jan., 25 to Mar. 7; from Mar., 1 to Apr., 4) and three cutting ages (28, 35 and 42 days) on dry matter production, tiller and bulk density of two cultivars of Panicum maximum Jacq. i.e., Guinea grass and Tobiatã. Plants were harvested in five vertical layers above soil level (0-20; 20-40; 40-60; 60-80; and over 80 cm). The sample was divided in: green leaves, green stem and dry material. Despite the higher productions of total dry matter and green leaves presented by cultivar Tobiatã, especially in the second growth period, "Colonião" presented higher bulk densities of total dry matter as well as green leaves. The N fertilization (50 kg N/ha/cut) increased the dry matter density of green leaves in both cultivars without changing the tiller density. Stem elongation was stimulated by N fertilization allowing a better distribution of green leaves in the upper layers of the canopy.