One of the pronunciation I struggle most is 「物」: more ofthen than not, I misread it in words like 「作物」 and 「薬物」. I know what they mean, but it's likely I misread them by reading 「もつ」 instead of 「ぶつ」 and the other way around.
I tried to find some criteria to understand how they are read, but in Google and my grammars I wasn't able to, so I was wondering if there is any criteria at all?
Unfortunately, there is no easy rule here, and the same is true for many other kanji. もつ tends to appear in the names of basic things that have been around for hundreds of years. ぶつ tends to appear in technical terms related to physics, chemistry, etc (物理学, 化合物, 薬物, 毒物, 物性). Anyway, the number of common words where 物 is read もつ is small, and it's possible for you to learn them all (食物, 書物, 貨物, 穀物, 宝物, 供物, 作物, 禁物).
