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Forage resources during late summer in semi-arid regions are limited, but this limitation could be alleviated by cultivating suitable crops. In this study three seeding rates of smooth vetch (Vicia dasycarpa cv. ’Maragheh’) and grass pea (Lathyrus sativus cv. ’Naghadeh local’) were tested as pure and mixed stands with shattered barley seeds that were harvested in mid-July from north-west Iran. Several agronomic and quality-related traits were determined when the legumes reached the flowering stage, which coincided with the initial creamy stages of barley. The choice of crop significantly (P < 0.01) affected dry biomass and crude protein. The highest dry biomass (9 t/ha) was obtained in a mixture of barley and vetch at 200 seeds/m(2). The highest protein levels (>20%) were obtained in pure stands of vetch and grass pea although the levels dropped to 18% in some mixtures with barley. The mixture of barley and vetch at 200 seeds/m(2) resulted in the highest land equivalent ratio (1.71) while the highest relative value total (1.35) was obtained from a mixed crop of barley and vetch at 250 seeds/m(2). Thus, a mixed crop of barley and smooth vetch at 200-250 seeds/m(2) is the best crop combination when planted as a summer crop in semi-arid regions.