Bushel is a measure of volume, while lbs is a measure of weight. So, it will depend on the density of your fertilizer. And each fertilizer (Dap, urea, P, K, etc.) will have different densities.
You can find the volume of a bu, so this web site has the Lbs per cubic foot listed for _one_ fertilizer of granular. Probably get you pretty close.
http://www.saskferco.com/fertilizer/urea.html
Below is a cut & paste (from a public University - credited, so should be ok) dealing with liquid ferts.
I didn't do the math for you, but you should be able to get there from here. /forums/images/graemlins/smile.gif
--->Paul
By the Gallon or by Weight?
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Fluid Fertilizers--Liquids and Suspensions
MSU Ag Facts
Extension Bulletin E-933, December 1984, Revised,
destroy previous editions
by R. E. Lucas and M. L. Vitosh, Department of Crop
and Soil Sciences
Most fluid fertilizer concentrates weigh 10 to 12 pounds
per gallon. Therefore, about 9 gallons of liquid are
required to provide the same quantities of nutrients as
100 pounds of dry fertilizer of the same formulation. If
the dry fertilizer costs $12 per hundred ($240 per ton),
the liquid fertilizer of the same formulation shouldn't
cost more than $ 1.33 per gallon. Fertilizers of the same
grade, formulation, placement and rates give nearly
identical response, whether liquid or dry.