Field and Laboratory experiments were conducted at the experimental Farm Station of El-Serw, Damietta Governorate and Seed Technology  Research Unit , Mansoura, during the season of  2013/2014 and 2014/2015,  to study the effect of potassium fertilization rates  e.g. 0, 15 K 30 , 45 kg K₂O and foliar spraying of some plant extracts i.e. rose water, mango and orange was used for spraying Berseem plants in each plot at flowering and seed filling stages to study the effect on forage and seed yield of berseem clover cv. Serw 1 as well as seed quality under saline soil condition. The experimental was arranged in strip plot design with three replicates. Potassium fertilizer rates were devoted in the horizontal plot whereas, the water and some plant extracts were assigned in vertical plot. The experimental plot area was 3x4 m². The results could be summarized  as follows: Adding potassium fertilizer rates in high portion (45 kg K₂O) markedly increased green ad dry forage yields when compared with the other portions i.e. 15 and 30 kg K₂O. in the first, second and third cut, respectively. The lowest value of green forage yields were observed under the control treatments (without fertilization). The highest number of heads/m², weight of heads/m² and no. of seeds/head, straw and seed yield kg/fed increased significantly in the two seasons when plots treated with the high portion of potassium fertilizer rates, while the lowest means of the above mentioned characters were observed in control treatments. In addition, 1000-seed weight, straw yield and seed yield kg/fed didn't reach the significance of differences in the first season. Spraying berseem with water and/or plant extracts achieved the highest mean of significance of differences in the second season for no. of heads/m², weight of heads/m², no. of seeds/head and 1000-seed weight , straw and seed yield/fed. when using orange plant extracts. With regard to seed quality, with increasing potassium application seed  and seedlings vigor traits as measured by accelerating aging test,  electrical conductivity of leached seed, seedling length, seedling dry weight and seed vigor index were the best comparing obtained seed from unfertilized plots with potassium. The studied plant extracts had significant effects on germination percentage, electrical conductivity, seedlings dry weight and seed vigor index meanwhile the effect on accelerating test and seedling length was insignificant.