Two field experiments were conducted at Kafr El-Hamam Agric. Res. Station, El- Sharkia Governorate in the two successive seasons of 2003/04 and 2004/05 to study the effect of three harvesting dates at the main plot  (140, 155 and 170 days after sowing), three plant densities (1750, 2000 and 2250 seeds / m²) for sub-plot and three farmyard manure treatments (0, 10 and 20 m³ FYM / fed.) for sub-sub plot, on yield quality and mineral content in seeds for flax variety(Sakha2). Results obtained can be summarized as follow: 1- Delaying harvesting date up to the oldest age (170 days from sowing) caused on increase in all straw and seed yield characters in addition to all mineral contents of flax seeds, except with fiber fineness trait which remarkable reduction had happened as resulted of delaying harvesting date. 2- There was gradual increase in  plant height, technical stem length, straw yield per fed., fiber yield per fed., fiber fineness, seed yield per fed.,  oil percentage and seed protein percentage. Meanwhile, all characters per plant in addition to 1000 seed weight decreased with increasing plant density towards 2250 seeds/m². But mineral content or percentage did not affected significantly in this case. 3- Straw and seed yields per fed and their related characters in addition to mineral content for seeds were increased but fiber fineness decreased with increasing farmyard application amount. D x H x FYM interaction was non-significant effect in all characters studied.