Fantastic stuff Arnoud!
I did try to play around with ta similar concept using the Landsat information (http://landsat.usgs.gov/) using the earth explorer app.
Mathematica is such a wonderful tool!
More details in the use of Landsat images.
http://www.nass.usda.gov/EducationandOutreach/Reports,PresentationsandConferences/Presentations/BoryanSeffrinJohnsonFASSeminar06.pdf
Is there any way to estimate the total bushels estimated from the area rather than a percentage?
Yes, but you need the geo position and the elevation of the drone/camera as well as the camera field of view, to compute the area that's visible in the image.
And an estimate of the "normal" yield in bushels for a given acre.
