I think you are quoting the wrong article, yours talk about attacking humanitarian aid, this one concerns free passage of food, is more relevant and it does not always apply
Mine talks about destroying greenhouses, fields, food, etc. as has in fact been done.
I'm thinking that as long as there's food, maybe you can destroy them, but if you then, having destroyed them while there is food, restricts the supply you are still breaking the treaty.
There's also article 54 §1 of additional protocol I.
https://ihl-databases.icrc.org/en/ihl-treaties/gciv-1949/art...
this is complex however, https://lieber.westpoint.edu/siege-law/