Leaf and tiller or stolon death ofLolium perenne, Agrostisspp., andTrifolium repensin set-stocked and rotationally grazed hill pastures

Abstract

Leaf and tiller or stolon death of Lo/ium perenne, Agrostis spp., and Trifolium repens in set-stocked and rotationally grazed hill pastures AbstractLeaf death rates, leaf longevity, and tiller and stolon death rates of Lolium perenne, Agrostis spp. and Trifolium repens were compared for one year on hill pastures which were set-stocked and rotationally grazed by sheep. Leaf death rates and leaf longevity were largely unaffected by grazing management, and the number oflive leaves per tiller or stolon did not differ greatly between managements. Agrostis spp. had more leaves per tiller than L. perenne. Leaf longevity was least in spring and summer when leaf death rates were fastest, and was greatest in winter when leaf death rates were slowest. In autumn, spring, and summer, mortality of leaves occurred within 3 weeks of their appearance, resulting in the loss of up to 28% of leaves which had been formed soon after one grazing before the next grazing under the rotational management. The long rotation in winter (63 days) resulted in the death of many leaves before they had a chance to be grazed. Leaf utilisation data showed that 20-46% of L. perenne leaf tissue, 45-63% of Agrostis spp. leaf tissue, and 34-60% of T. repens leaf production was ungrazed and subsequently died and decayed. Grazing pressure is critical in determining the amount of leaf tissue entering the litter pool, and has a considerable influence on tiller and stolon death.

Effects of spring defoliation and fertilizer nitrogen on the growth of white clover in ryegrass/clover swards

“…Some aspects of white clover growth changed in relation to the total herbage mass accumulated in the different treatments. Rates of leaf appearance tended to rise with increasing temperatures, as in other investigations {Wilman and Asiegbu, 1982b;Chapman et al, 1984) but also responded negatively to accumulating herbage mass {Table 6; Figure 4a). As mass accumulated In May and June and the older clover leaves in all treatments began to die off, the number of green leaves retained per stolon showed an inverse relationship with herbage mass (Figure 4b).…”

Demografia do perfilhamento e taxas de acúmulo de matéria seca em capim 'Tifton 85' sob pastejo

“…Isto se deve ao maior número de perfilhos em um determinado período poder ser compensado pelo maior peso dos mesmos em outros períodos (Westoby, 1984;Matthew et al, 1995). Além disso, há situações onde a maior parte dos perfilhos existentes em um dado período pode ser composta por perfilhos recém-surgidos que são importantes em termos de demografia, mas que contribuem pouco para a massa de forragem do pasto (Chapman et al, 1984).…”

“…A principal causa da morte de perfilhos vegetativos é o sombreamento de pequenos perfilhos devido ao aumento da massa de forragem no relvado (Ong et al, 1978;L'Huillier, 1987). Já a principal causa da mortalidade de perfilhos reprodutivos é atribuída ao pastejo, pois quando uma pequena porção do caule é removida pelos animais durante essa fase de desenvolvimento da planta, o perfilho todo morre (Chapman et al, 1984;L'Huillier, 1987).…”

Improving the McCall herbage growth model

“…2). Woodward ( 1998b), using data reported by Chapman et al ( 1984), fitted the function: Leaf death rate = 0.00158 × (T soil + 2.2) in kg/kg per day; where T^j, is 100 mm soil depth temperature. This implies that llS (in kg/kg per °C-day) has a positive and curvilinear relationship with soil temperature:…”