Influence of sward condition on leaf tissue turnover in tall fescue and tall wheatgrass swards under continuous grazing

Abstract

Two experiments were carried out on a tall fescue sward in two periods of spring 1994 and on a tall wheatgrass sward in autumn 2001 and spring 2003 to analyse the effect of sward surface height on herbage mass, leaf area index and leaf tissue flows under continuous grazing. The experiment on tall fescue was conducted without the application of fertilizer and the experiment with tall wheatgrass received 20 kg P ha )1 and a total of 100 kg N ha )1 in two equal dressings applied in March (autumn) and end of July (midwinter).Growth and senescence rates per unit area increased with increasing sward surface height of swards of both species. Maximum estimated lamina growth rates were 28 and 23 kg DM ha )1 d )1 for the tall fescue in early and late spring, respectively, and 25 and 36 kg DM ha )1 d )1 for tall wheatgrass in autumn and spring respectively. In the tall fescue sward, predicted average proportions of the current growth that were lost to senescence in early and late spring were around 0AE40 for the sward surface heights of 30-80 mm, and increased to around 0AE60 for sward surface heights over 130 mm. In the tall wheatgrass sward the corresponding values during spring increased from around 0AE40 to 0AE70 for sward surface heights between 80 and 130 mm. During autumn, senescence losses exceeded growth at sward surface heights above 90 mm. These results show the low efficiency of extensively managed grazing systems when compared with the high-input systems based on perennial ryegrass.

Canopy Height and Nitrogen Affect Herbage Accumulation, Nutritive Value, and Grazing Efficiency of ‘Mulato II’ Brachiariagrass

“…In a Marandu palisadegrass pasture maintained at 30 cm under continuous stocking and fertilized with 0, 150, 300, and 450 kg N ha -1 yr -1 , the LAI was increased by 100% when N rate increased from 0 to 450 kg ha -1 yr -1 (Pereira et al, 2014). Reduction in GE with lesser grazing intensity has been reported for tall fescue (Agnusdei et al, 2007;Braga et al, 2007;Smart et al, 2010;Penati et al, 2014). Reduction in GE with lesser grazing intensity has been reported for tall fescue (Agnusdei et al, 2007;Braga et al, 2007;Smart et al, 2010;Penati et al, 2014).…”

“…Stapf, 'Marandu'], and cultivar Tanzania guineagrass (Panicum maximum Jacq.) (Agnusdei et al, 2007;Braga et al, 2007;Smart et al, 2010;Penati et al, 2014).…”

Effects of Grazing Pressure on Efficiency of Grazing on North American Great Plains Rangelands

“…Penning et al (1991) showed that perennial ryegrass (Lolium perenne L.) pastures grazed to maintain a 1.0 LAI had 27% less dead stem mass and 45% more vegetative tillers than swards of 2.0 LAI. Others also documented that grazing efficiencies are greater on swards maintained at lower sward canopy height or LAI and attributed this phenomenon to lesser amounts of accumulated senescent vegetation in the shorter swards (Parsons et al 1983;Heitschmidt et al 1989;Mazzanti and Lemaire 1994;Nakatsuji et al 2006;Agnusdei et al 2007).…”

A Comparative Analysis of the Temperature Response of Leaf Elongation in Bromus stamineus and Lolium perenne Plants in the Field: Intrinsic and Size-mediated Effects

“…The comparison of LER responses can be complicated (obscured) by tiller size effects. This is because of positive relationships between tiller size and LER, as revealed by grazing experiments with control of sward state for several C3 forage grasses (Bircham and Hodgson, 1983;Mazzanti et al, 1994;Agnusdei et al, 2007). The origin of this effect is not clear, although it seems to be related to an influence of the length of the sheath tube through which the growing leaf emerges on the length of the leaf growth zone (Casey et al, 1999;Kavanová et al, 2005).…”