This study was conducted to investigate the effects of planting date, foliar application of benomyl fungicide and potassium silicate in improving the quality of soybean (cv. Williams) seed in Gorgan during 2011 and 2012. In the first year (2011), the experimental treatments were including planting dates (April 20, May 13, June 3, June 29 and July 22) and foliar application of benomyl fungicide (used at R3 + R6 or unused) and in the second year (2012) were including planting dates (May 1 and July 7), foliar application of benomyl fungicide, silicon (Si) and silicon + benomyl. Water-soluble potassium silicate as silicon supply, in three stages (V6, R1 and R4), at the concentration of 40 grams per liter was sprayed on the leaves. The results showed that an increase in air temperature during seed filling period (R5-R7) in the early planting dates is the most important factor in reducing seed quality. Also, a significant negative correlation was observed between seed infection by Phomopsis sp. and Nigrospora sp. and seed germination and vigor. Delayed planting by reducing the temperature during seed filling period and seed infection by this pathogenic fungi, increased seed quality. Foliar application of benomyl fungicide and potassium silicate by reducing seed infection by pathogenic fungi, improved the quality of soybean seeds. Thus, the delay in planting of precocious cv. Williams, foliar application of potassium silicate and benomyl fungicide in reproductive stages can be advised as the strategies to enhance the seed quality of this cultivar to the farmers and seed producers in Gorgan.