Three experiments were conducted with Medicago polymorpha collected from a diverse range of sites in Sardinia, to investigate the relationship between edaphic and environmental conditions at collection sites, and the growth and nodulation of the genotype. Growth response to 2 temperature regimes (20/15�C, 11/9�C) was greater for genotypes collected from high altitude than for those from 1350 m. Shoot yield was more depressed by low temperature and more stimulated by high temperature in high altitude than low altitude genotypes. All genotypes nodulated when exposed to considerable acidity stress (pH 5.4) and 1 mmol Ca/L in solution culture. However, there were differences between genotypes in nodulation reduction caused by exposure to acidity. These differences were not well related to the soil pH at the site of collection, or to the effects of pH on the ability of root exudates from the genotypes to stimulate nod gene expression in Rhizobium meliloti.

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In semi-arid areas, forage crops for grazing are suitable for extensive, marginal lands because they can sustain competitive meat or milk production, they protect against soil erosion risks, and they can form the basis of an alternative sustainable agriculture. Drought is the main limiting factor to plant growth in these lands, seriously affecting total herbage production and seasonal availability of forage. Recent research work looking for new cultivars of some annual self-reseeding pasture crops (annual rye grass, lupin and subterranean clover) with an enhanced capacity for herbage or seed production under water stress, has demonstrated the difficulties in obtaining new cultivars of well adapted crops with substantial yield improvement under drought conditions. New management strategies for improving pasture availability for grazing and self-reseeding ability have been tested (also at farm level) showing clear possibilities for enhancement of herbage production and a more regular seasonal distribution in drought-prone environments.

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