The later you wait, the harder it is to dry for proper fermentation. Yields tend in the 1.5 to 4 tons dry matter depending on nitrogen and rainfall. For this yield and quality, drill into minimumly tilled corn ground in late August or early September. Harvest in the boot stage. Wheat is the latest, and gives the longest harvest window.
Rye is the earliest with the shortest window.
Triticale is in between. Stage of maturity at harvest is more important than variety choice. After heading out, these are low quality at best. Remember, first year corn is really inexpensive to grow. Second year corn isn't bad.