Vegetation Changes in Sown Grassland in the UK after Nine Years of Extensive Grazing Management

The effect of extensive grazing management with sheep on vegetation change in sown pastures (initially containing Lolium perenne and Trifolium repens) in the uplands of Scotland was investigated from 1990-1999. One treatment was representative of current more intensive management systems; it was fertilized, and maintained at a sward surface height of 4 cm. Two treatments were unfertilized and were maintained at sward surface heights of 4 cm or 8 cm; the ewe numbers carried on these treatments averaged 74% and 44%, respectively, of those on the fertilized treatment. In all treatments the sheep were Scottish Blackface ewes. Their single lambs also grazed from May until weaning in mid-August. Over 9 years there were only small changes in species composition in the unfertilized treatments. The changes were primarily shifts in abundance of the species present initially, with only a few additions or losses of species. L. perenne made a similar contribution to cover in both the 8 cm and fertilized swards. The highest content of T. repens was in unfertilized swards and the least was in the 4 cm fertilized swards. This study demonstrates that the contribution of the sown species to sward composition remains high in grazed upland swards that are more extensively managed for nearly ten years. Since there was little overall change in species composition, it could be difficult to achieve increased plant biodiversity in these systems simply by removing fertiliser and reducing grazing intensity

Grazing management strategies for Urochloa decumbens (Stapf) R. Webster in a silvopastoral system under rotational stocking.

Our objective was to compare herbage accumulation and nutritive value of Urochloa decumbens (Stapf) R. Webster managed under pre-grazing canopy light interception (LI) targets of 90%, 95% and 100% in silvopastoral system (SPS) and 95% in open pasture (OP; U. decumbens under full sunlight) to establish a pre-grazing target for SPS of ~43% shade. The evaluations were made during two rainy seasons and one dry season. The total herbage accumulation in SPS was lower than in OP at all LI targets and seasons. However, the difference in total herbage accumulation between SPS and OP was reduced when SPS was harvested at 95% LI, with reductions of 20% and 28% in both rainy seasons (12,191 × 15,324 kg DM/ha and 11,158 × 15,424 kg DM/ha respectively). Moreover, under 95% LI in SPS, crude protein concentration was 18% and 19% greater than that in OP in both rainy seasons (155 × 131 g/kg DM and 144 × 121 g/kg DM respectively), thus representing the optimal pre-grazing LI target for U. decumbens in SPS. In addition, a canopy height of 20 cm was necessary for 95% LI in OP and a height of 40 cm in SPS. Therefore, U. decumbens should be grazed at 40 cm canopy height, in SPS with ~43% shade to keep 95% LI as the target. However, this target will only be effective if the shade level is maintained, which will reduce height variation over time

Extensive Management of Sheep Grazing in Upland Sown Grassland: Long-Term Effects on Plant Species Composition

Changes in the Common Agricultural Policy have led to the development of agri-environment schemes to deliver environmental goods from grasslands. These schemes encourage more extensive grazing systems, and change the emphasis from animal output to issues such as increasing biodiversity. Lower stocking densities are expected to promote the development of a heterogeneous habitat and associated compositional changes in plant species. The long-term effect of more extensive sheep management, combining cessation of fertiliser and lower grazing intensity, on botanical composition and animal output in upland sown grassland has been studied at 3 sites (Marriott et al., 2002) since 1990. We describe changes in vegetation at one site between 1990 and 2004