Abstract
Abstract: The objective of this work was to evaluate the variations in root dry matter mass (RDM) and the percentage distribution (PD) of the root density of Florico grass (Cynodon nlemfuensis) in the 0-40-cm soil layer, when managed under different grazing strategies. Two defoliation frequencies (90 and 95% light interception, as the criterion for allowing animals in the paddock) and two defoliation severities (post-grazing heights of 20 or 30 cm) were assessed. Four seasonal evaluations of the root system were performed between the winter of 2012 and the autumn of 2013, using the monolith and trench excavation technique, collecting 1-dm3 samples from soil surface down to a depth of 40 cm, in four sequential extracts of 10 cm each. Lower RDM values (0.69 g dm-3) were obtained in winter, with the four grazing strategies, whereas higher values were observed in spring (1.64 g dm-3), for the 30-cm post-grazing residue, and in autumn (1.63 g dm-3) for the 20 cm post-grazing residue, regardless of the light interception value. Between 52 and 66% of the RDM density was observed in the 10-cm layer, for all four grazing strategies, in all seasons.
Highlights
Pastures occupy approximately one-quarter of the Brazilian territory and are the cheapest food source for ruminants
Variations in root dry matter mass (RDM) and percentage distribution (PD) of the root density of Florico grass, managed using four different pasture strategies, were consistent with the management strategy applied to the shoots because of the close relationship between the aerial and the underground components of pasture growth, where the root is the source of energy and the shoot is a drain on the organic reserves (Rodrigues et al, 2007; Silva et al, 2015)
The pre-grazing canopy height was affected by the light interception (LI) in the spring, with greater heights observed at 95% LI in treatments with a post-grazing residue (PGR) of 20 or 30 cm (Table 3)
Summary
Pastures occupy approximately one-quarter of the Brazilian territory and are the cheapest food source for ruminants. In the search for highly productive forage species for ruminant feed, the grasses of the genus Cynodon have been focused on because of their versatility and flexibility in use (Carvalho et al, 2012). Florico grass is highly productive and it adapts to different climate and soil conditions; it is more resistant to changes in the employed management practices (Rodrigues Filho et al, 2000). Cynodon nlemfuensis or star grass shows more developed stolons and fewer rhizomes than other Cynodon species. It is a rustic, persistent plant that is adapted to different climatic conditions (Pedreira, 2010); it has a higher fertility requirement than other grasses
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