Tillering and forage accumulation in Marandu grass under different grazing intensities

Abstract

Studies of plant responses to defoliation are important to develop pasture management strategies. The objective of this study was to evaluate the population density of basal, aerial and reproductive tillers, tiller appearance and mortality rates, forage accumulation and sward structure in Marandu grass pastures under different grazing intensities. The experimental period was from January to June 2006, divided in three seasons: summer, autumn and winter. The pastures were continuously grazed using variable stocking rates. The grazing intensities corresponded to 15, 30 and 45 cm of sward height. The experiment was arranged in a complete randomized block design with three treatments and two replicates. The sward heights were measured twice a week. The response variables were: forage accumulation, forage mass and its morphological components; and population densities of basal (TPDb), aerial (TPDa) and reproductive (TPDr) tillers. The highest TPDb (P > 0.05) was recorded for the shortest sward pasture, and the highest TPDr (P<0.05) for the tallest sward pasture. Swards showed a tiller size/density compensation mechanism and, consequently, the forage accumulation was similar (P > 0.05) among the grazing intensities. Pasture with a sward height of 35 cm had 94% of sun light interception. The highest variations in forage accumulation and sward structure were more influenced by seasonal differences than by grazing intensities. Pastures of Marandu grass showed large flexibility in grazing management, which allowed it to be maintained at sward heights between 15 and 35 cm.

Grazing intensity affects forage accumulation and persistence of Marandu palisadegrass in the Brazilian savannah

“…In the first 2 years, the values for TPD (Table ) were in line with the general pattern of low tiller populations with tall canopies and high tiller populations with short canopies subjected to continuous stocking management (Calvano et al, ; Matthew, Lemaire, Sackville‐Hamilton, & Hernández‐Garay, ; Sbrissia & Da Silva, ). This is essentially a consequence of competition for light (Sackville‐Hamilton, Matthew, & Lemaire, ) since reduced light availability at the base of the canopy is one of the main factors interfering with the tillering process of canopies grazed leniently.…”

“…From December 2005 to September 2006, Marandu palisadegrass pastures were grazed under continuous stocking by cattle for target canopy heights of 15, 25 and 35 cm (Calvano et al, ). From then, the canopy height was monitored on a weekly basis, and the average canopy heights were 14.2, 28.5 and 41.8 cm (for target heights of 15, 30 and 45 cm) in December 2007.…”

Canopy height and N affect herbage accumulation and the relative contribution of leaf categories to photosynthesis of grazed brachiariagrass pastures

“…Variations in HAR and HA in response to canopy height have been reported for both tropical and temperate grasses (Baker, Le Du, & Alvarez, 1981;Hernandez-Garay et al, 2014;Paula et al, 2012;Wright & Whyte, 1989). In some cases, greater HAR and HA have been measured in taller canopies (Carloto et al, 2011;Flores et al, 2008) although Canto, Jobim, Gasparino, and Hoeschl (2008) reported that for (Calvano et al, 2011;Pequeno, 2010). The lack of responses to a range of canopy heights has been associated with grass flexibility in terms of grazing management under continuous stocking.…”

“…For some brachiariagrasses, the canopy height did not affect HAR or HA. Marandu and Xaraés palisadegrasses (both of them brachiariagrasses) showed similar HA and HAR when canopies were kept at 15, 30 and 45 cm by continuous stocking (Calvano et al., ; Pequeno, ). The lack of responses to a range of canopy heights has been associated with grass flexibility in terms of grazing management under continuous stocking.…”

Sheep production during the rainy season in marandu palisadegrass swards previously utilized under deferred grazing

“…After mowing, due to the high amount of dead forage on the plants, there may have been a lower incidence of light on the basal buds, with consequent delay of tillering (Calvano et al, 2011;Santos et al, 2011). In addition, with the mowing, many dead and old tillers were eliminated from the forage canopy.…”