Rule of Thumb on Drought Corn Silage
1) Expect 1 ton of 35% dry matter silage for each 5 bushel of corn grain (estimated), so 40 bushel corn would give you nearly 8 ton of silage per acre, or
2) Corn with few ears, expect 1 ton of 35% dry matter silage for each foot of corn plant height, plant height minus the tassel length. SO, 7 feet tall corn minus 1 foot of tassel height = 6 feet or about 6 ton per acre.
Below is a spreadsheet that is helpful for valuing silage. Go to AgManager.info for custom rates to fill in the spreadsheet. Replace the numbers in blue with your figures, costs, etc.