How to restore farms?

[Connacht 0]

I mark farm tiles as historical as soon as they appear, but I forgot to check the box for one. Now a small industry appeared in its place. If I destroy it, the farm never returns, only industries. I can untile, but then there is a hole in the crop field. Is there a way to make it become farm again, without having to destroy everything and try to form again the farm from scratch? Many thanks!

[CorinaMarie 29,923]

27 minutes ago, Connacht said:

... destroy everything and try to form again the farm from scratch?

It's been a very long time since I played 3000 so take this devastating news with a grain of salt.

Afaik, when regular industrial starts taking over the crop field it's because the pollution threshold has been exceeded. I also seem to recall there's a minimum size in which a farm will grow. I believe you will need to bulldoze the entire farm leaving only the zoning, but also bulldoze any encroaching roads or other development to lower the local air pollution.