Distribute a 10-10-10 fertilizer at the rate of 8 ounces per grape vine, in the area around each grape vine. Stay 6 to 12 inches clear of the plant's stem and go out at least 18 inches, or far enough to cover the area beneath the vine's spread.
Soak the area with water to push the fertilizer into the soil and to the roots of the grape vines.
Apply double the amount (16 ounces) in the next year at the end of April or beginning of May.
Increase the amount of fertilizer to 24 ounces per grape vine in the third and all succeeding seasons.