I'm all confused.
A bu is a unit of volume. It is always the same _size_, but it can and does vary greatly in weight.
Since everyone who buys or sells cares about quality & has a scale, we really don't use that volume thing anymore. Back in the old day, they didn't have a good scale, & sold by the uniform bushel - volume.
A good bu of wheat has been determined to weight 60 lbs. That is the standard conversion.
However, we weight the crops these days on a scale.
We check the test weight. (There are little cans that you fill exactly level full, and percicely weight, then look on a chart to figure out how much an exact busghel would really weigh.)
We check the moisture. (Put it in a little metal pot with electical probs, figures out how much moisture is in it.)
They take these numbers, and adjust the grain to become a 'perfect bu' of grain. They deduct money if it is too wet, or deduct money if it is too light weight. Rarely do you get a bonus if it is too dry or weights more that 'perfect'.
Wheat & soybeans are considered to be 60 lbs per bushel.
Shell corn is considered to be 56 lbs.
Ear corn is considered to be 72 lbs. (The cobs add 16 lbs, and ear corn takes up about 2x the volume of a shelled bushel.)
Oats is considered to be 32 lbs (tho many buyers require 34, or even more test weight to get top dollar).
So, a bushel is a volume measurement, and we most all sell on a weight basis these days, so these numbers were settled upon to give us a way to compare.
It is very odd for prices it be based on volume (per bu) but we sell by weighing the crop (per lb). But that is how it is.
--->Paul