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SUMMARYThe response of two cultivars of white clover (Aberystwyth SI 84 and New Zealand Grasslands Huia), grown under laboratory and field conditions, to inoculation with two endophytes (Glomus mosseae LI and Glomus etunicatus) was investigated in two hill soils with various amounts of added phosphate.In the experiment with the deep peat soil in the laboratory, inoculation with either endophyte increased infection from 2 % to up to 70 %, the increase being less the higher the amount of added P. Shoot growth of white clover was significantly increased (P < 0-05) by inoculation at the 0 and 20 kg P ha"' level and decreased at the highest level of added P (200 kg P ha~'). Both endophytes produced similar effects. With the brown earth soil, total infection of roots with indigenous endophytes ranged from 30 to 50 % and this was significantly (P < 0-05) increased by inoculation only at 40 kg P ha"'. However, the introduced coarse endophytes had replaced between a quarter and a half of the predominantly fine indigenous endophyte at each level of added P. This change of endophyte was without significant effect on dry wt of shoots and roots although there was a general trend for inoculation, and with Glomus etunicatus more than with Glomus mosseae LI, to increase shoot and root dry wt. Inoculation also tended to increase the P content of shoots and roots but this was statistically significant only at 40 kg P ha~'.In the field experiment with the deep peat soil, inoculation with Glomus mosseae LI doubled the amount of infected root from 18 to 42 % but there was no effect on shoot growth or the concentration of P. With the brown earth soil, although the amount of infection was not increased, the introduced coarse endophytes had become established in the roots but no effect on shoot growth was observed in the year of sowing. However, in the first harvest year, in the presence of 40 kg P ha~', clover inoculated with Glomus etunieatus produced double the amount of dry shoot per hectare produced by uninoculated plants and 75 % greater than that produced with Glomus mosseae LI.These observations encourage the view that inoculation with mycorrhizal fungi of white clover for improved hill pastures might have a practical role if the responses could be made more predictable. It is concluded that further work is justified to understand the ecology of mycorrhizal fungi in hill pastures and how the symbiosis functions, to select suitable endophytes and to develop methods of inoculation appropriate for use in routine field practice.

In concluding the 1968 Symposium on hill land productivity (56), which has been taken as the starting point for this survey, the late Dr William Davies requested that someone prepare a blueprint for the overall development of hill lands and, more specifically, a scheme for agriculture which should include the full integration ot known facts into whole viable systems of husbandry. Since then, Walsh and Lee (111) have proposed a systems strategy for marginal land based on the concept of integrating oflF-farm feed energy with hill rough grazings, while Eadie (31, 32, 33) has proposed a 'two-pasture' year-round grazing system for sheep. The former scheme requires the provision of large areas of better quality land for conservation of herbage, or the buying of considerable quantities of feed which may not be economically feasible in all circumstances in hill areas of Great Britain. The 'two-pasture' system was designed to overcome the ecological deficiencies of traditional systems (24, 25, 30) and it has been shown to succeed in two highly contrasting environments (34, 35). A similar kind of approach is currently being tried in other areas (53, 97, 108).The most important single factor which influences animal output from the hills is nutrition and, although it is more critical prior to mating (50), iri late pregnancy (101) and during lactation (89), it needs to be improved throughout the year if output is to be increased. The key to an improved nutrition cycle for the grazing animal lies in pasture improvement.The development of successful whole-farm systems of hill sheep farming which depend on pasture improvement justifies a review of the present state of techniques for improvement and the identification of gaps in our knowledge.In addition to the above considerations:1. There is an increased awareness of the pressures of population growth on food supplies, coupled with the annual loss of approximately 20,000 hectares of good quality arable land. Wider discussion on the national needs for the improvement of hill-land use (1, 7, 52, 84) and of the particular needs in Scotland, with the largest proportion of hill land in Britain (103), has stimulated renewed interest in this subject.2. The impact of the world energy crisis on thoughts about the energy budgets of agriculture (17, 104) has indicated new grounds for supporting meat production from the hills and uplands (105). 3. The world meat shortage emphasises the importance of livestock. Although the hills produce only 7% of the total monetary agricultural output in the United Kingdom, they contribute 30% of the store sheep and 15% of the store cattle. Cunningham and Ashton (26) have recently calculated that at least 0*5 million hectares of good quality lowland would be needed to produce this output. Even if this land was available, the capital cost of preparing it for intensive livestock rearing would be immense. 4. There has been increased interest in recent years in the development of improved methods for assessing the economics of farming systems (51, 69, 70) a...

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