Should the standard of review under a Michael Morton act violation be abuse of discretion or de novo? There was discovery order on file, prosecution did not turn over a bill of sale that explained why defendant had possession of a tractor that was allegedly stolen. Showed it on day one of trial, was not admitted into evidence, but many objections and error preserved.

De novo- statute was not followed
Abuse of discretion- judge should have stopped trial and let defendant have time to look at bill of sale and decide how best to use.

If the court was not called upon to make any ruling concerning the admissibility of the evidence, then there is no abuse of discretion involved. What error do you think was preserved?

The Bill of sale was never handed over to the defense. The actual Bill itself.
The judge doesn't allow it to be admitted but, there is much discussion about it, in front of the jury. The defense states on the record that they never received it and it is in violation of the Michael Morton Act.

The deputy also makes statements saying the bill of sale looks like the handwriting of the defendant, but there is no objection.

had the Bill been handed over, the defense could have brought in their own handwring experts and determined it's validity.

The MMA says nothing about sanctions or how violations should be dealt with. So the answer to your question is not found there. As best I can tell, you are possibly referring to a violation of Brady (or subsection (h)). The Brady cases should thus answer whether there was any reversible error. If the defendant received a bill of sale, then I assume its existence and contents were known to him.