Crop goes backwards

Hi,

My crop levels are all level 15. But at some point my production became less. And now my crop goes backwards, namely -237 per hour.
I don't really understand this. What can I do to make that stop?
And what caused this?

Thanks for helping!

Your troops need crop to survive and they decrease your crop production. Occupy crop oasises if you want to increase it.

Your troops need crop to survive and they decrease your crop production. Occupy crop oasises if you want to increase it.

Ah, thank you!
Didn't know that..

Its no big deal to be negative, Id recommend running -30k at least in all cities, it's easy to maintain and gives you a big army