Herbage yield in Signalgrass pastures as affected by grazing management

Abstract

Signalgrass is largely planted as cultivated pasture in Brazil, but no management targets have been identified. The objective of this study was to evaluate daily herbage accumulation rate (HAR) in Signalgrass pastures grazed at two intensity x two frequency treatments using steers. Target intensities corresponded to 5 and 10 cm post-graze sward height and frequencies were determined by pre-graze sward light interception (LI = 95 or 100%) by the canopy. The trial was carried out from January 2007 to April 2008 on an Entisol. Less frequently grazed pastures had higher HAR during the entire period (29 and 36 kg/ha for 95 and 100%-LI, respectively). There was no intensity effect on HAR, except in the 2007 summer season (January to March) when pastures grazed to 10 cm had a higher HAR (59 kg/ha) than those grazed to 5 cm (45 kg/ha). Total leaf yield increased when regrowth was longer (7930

vs. 8729 kg/ha for 95 and 100%-LI, respectively), but stem and dead material yield increased as well (4877 vs. 7155 kg/ha for 95 and 100%-LI, respectively). The advantages of extending the rest period due to increased HAR was counterbalanced by the great influence of stem and dead material, decreasing pasture leafiness and likely forage nutritive value on the grazed stratum.