While a nice theory, this is not competitive in practice... The capital costs and loss in productivity result in about a 2 to 3 times lower profit per unit of land compared to full solar. Just put solar on the non-ideal fields (iirc about 4% of German AG area would be needed to cover electricity demand with solar)
You miss the point that identically the same land is now producing two revenue streams, one year-round. And, that ag yield is increased. Fortunately, they don't need your approval. It is being done now. Japanese are leading.
It might not need to be 100% of fuel used, subsidizing the fuel supply would be enough I think. It would also allow those farms to claim some of that as carbon credits and other green certificates.
