In Korea, silicate has generally been fertilized once (at the first year) during the 4 years (S4-P1 condition) to improve the yield of rice. However, because the amount of available silicate in soil has been chronologically decreased, we could not expect the effects of silicate on improvement both of yield and of quality in rice grain from the third year after fertilization. In this study, we investigated the effects of silicate fertilizations with various periodic conditions. To establish the condition of reasonable silicate fertilization to improve the high quality of rice, we examined the effects of silicate fertilization, the improvement of rice grain quality, characters of nutrient adsorption and the amounts of available silicate in soil with or without the restoration of straws. We fertilized the 130mg/kg (the amounts for 4 years which encouraged by Korean Rural Development Administration) of silicate with three different conditions including i) S4-P1: once fertilization at the first year during 4 years, ii) S4-P2: twice fertilization every 2 year during 4 years and iii) S4-P4: four times fertilization each year during 4 years and then we performed the experiments until the third years. When we fertilized the silicate concurrently with the restoration of straws, the yield of rice was increased around 8~20% in general. In S4-P1 condition, the yield was significantly decreased chronologically and in S4-P2 condition, the yield was shown to increase from the third year because silicate was fertilized again at the second year. Furthermore, in S4-P4 condition, the yield was slightly increased every year. The contents of amylase and proteins, known as the index of palatability, were not much significantly changed by any different condition. However, the ratio of Mg/K, known as the index of rice stickiness, was increased with the fertilization of silicate. The absorbed amount and utilized coefficient of nitrogen and silicate in plants was much high in straw-restored condition in comparison with in non straw-restored condition and utilized coefficient of nitrogen and silicate was high in order with S4-P1> S4-P2> S4-P4. The amount of available silicate in soil was higher in straw-restored condition than in non straw-restored condition. In S4-P1 condition, the amount of available silicate in soil was significantly decreased chronologically and in S4-P4 condition, the amount of available silicate in soil was slightly increased every year.