Two field experiments were conducted at the Research Farm of Faculty of Agriculture, Suez Canal University at Al-lsmailia during 2003/2004 and 200472005 winter seasons. The present investigation aimed to study the effect of sowing date, different rates of phosphorus fertilization and biofertilization with Phosphoren on seed yield and its attributes of berseem multi-cut (Meskawi) Helaly cv. in sandy soil under sprinkling irrigation system. A split-split plot design with four replicates was used in both seasons. The results revealed that early sowing date (5“ Oct.) increased significantly number of stemsfplant, number of heads! 10 plants, seed weightl10 plants (9) , 1000— seed weight (9), seed and straw yields in both seasons. Concerning seed yield (kgifad), the superiority of the first sowing date (5th Oct.) over the second (20”1 Oct.) and the last sowing date (44th Nov.) reached 8.19% and 14.74% in the first season and 11.97% and 18.93% in the second season, respectively. In general, increasing the levels of phosphorus increased significantly seed yield and its attributes. Applying P fertilizer up to 31.0 and 46.5 kg P2057fad to clover plants increased seed yield about 19.79 and 26.12% in the first season and about 20.20 and 26.28% in the second season, respectively, compared with 15.5 kg P2057fad. Phosphoren had significant favorable effects on all traits. Seed yield Kgffad and straw yield toni'fad increased significantly by 5.84 and 5.72% in 200372004 and by 6.39 and 6.93% in 2004/2005 seasons, respectively, Compared with untreated plants. The treatment combination of 46.5 kg P2057fad and Phosphoren increased significantly seed yields by 31.92 and 32.77% in 2003/2004 and 200472005 seasons, respectively, in comparison with treatment combination of 15.5 kg P2057fad and without Phosphoren. Seed yields in both seasons were positively and highly significantly correlated with number of stems/plant, number of headsl10 plants, seed weighU10plants (g), 1000-seed weightlg), specific seed weight, seed and straw yields. Path analysis of both seasons showed that seed weight! 10 plants (9) and its interaction with 1000-seed weight (g) and number of heads! 10 plants were the main source of yield variation. The direct effects were 37.49, 25.37 and 11.69% in the first season and were 25.25, 21.96 and 16.52% in the second season, respectively,.