Is there any chance of Sprinkler spraying liquid（water? or other liquid）to boost plant growth randomly,just like rich soil in
FarmersDelight? I think it will make it more valuable.

True, the use cases of the sprinkler are edge cases right now, to be honest I only created it for the neapolitan compatibility.
But I also designed them to be easily extended with additional functionality.

Boosting crop growth could certainly be a good feature, but I would like it to be boosted by some sort of liquid fertilizer and not just water

I have just realised that sprinklers already hydrate farmland, since farmland gets slowly hydrated in the rain, and a sprinkler with water simulates the rain

Would it be possible for the sprinkler to hydrate farmland? It would be cool for greenhouses.

Added liquid fertilizer in 1.1.0 which can be used to boost crop growth