The hills and uplands lie within the poorer ‘less favoured’ soil and climatic areas which account for almost 10 M ha of the UK's 19 M ha of agricultural land. Rough grazing comprises 6 M ha. Dry matter (DM) production from native hill swards, governed by soil type, climate and species composition, typically ranges from 1 to 5 t per ha, and is highly seasonal. The best grade of native hill sward is the bent-fescue (Agrostis/Festuca) association. Upland permanent pasture sward production is strongly influenced by the proportion of perennial ryegrass and level of fertilizer N input; typically, DM production ranges from 3.5 to 91 per ha.
Constraints to herbage production include acid soils, impeded drainage and shortage of major plant nutrients particularly N and P. Deficiencies of some major nutrients and of trace elements in the plants can consequently have serious implications for livestock performance. Relationships among trace elements are particularly complex. The climate is severe and highly variable, with low temperatures, exposure to wind, high rainfall and frequent winter frosts being notable features. Bracken, rush, gorse, broom and scrub woodland communities are special vegetation problems which adversely affect pasture production and utilization.
Specific improvement techniques for the differing soil type — plant community associations are available but economic considerations are important when making the choice and deciding on the extent of improvement. Addition of lime and fertilizers, and the introduction of improved grass species and white clover, are the keys to enhanced sward production and quality. Maintenance of soil fertility is essential to ensure continued production. White clover is particularly important for animal nutrition and for its ability to contribute to available soil N via rhizobial N fixation. However, fertilizer N has a role in strategically extending the grazing season and for intensifying winter feed production (silage or hay) from suitable land; silage offers the better option.