Maximum crop outputs
1. Without crop enhance and no crop oasis
2. With crop enhance and no crop oasis
3. Without crop enhance and crop oasis
4. With crop enhance and with oasis
Note - This will be calculated with level 0 planting tech - if you wish to calculate these values for yourself at other technology levels, either message me and i will send you them, or just multiply these figures by 1+(0.1*your planting tech level)
Situation 1 - Without crop enhance and without any crop oasis

Situation 2 - With crop enhance and without any crop oasis

Situation 3 - Without crop enhance and with lv 9 crop oasis

Situation 4 - With crop enhance and with lv 9 crop oasis

Lets give an example that this will be useful for - If you are level 16 with level 10 planting tech and have lv 15 crop output in each of your cities (without enhancements), and are able to maintain an army with a 10 hour starving time, take the value given in table 3 - 60320, and double it due to the level 10 planting tech (120640). This means that you could maintain 12,064 cats, or 30,160 cav, or even 20,000 cav and 20,320 archers without even having a negative crop output. However when you include the 10 hour starving (losing 44000 an hour), this adds another 44000 troops that can be added to your army PER CITY that you want to risk. This means that at level 16, where you can control up to 6 cities, you can have a total army that can consume up 384,640 crop an hour! This means that you could maintain a 38k cat army with a 10 hour starve, or even have 96,160 cav.
In addition to this, if you were to have crop enhancements enabled on all your cities (which is advisable if you can defend your sub cities and will not lose them to other players), then this would further increase to 424,960. The possibilities are endless!
Of course the main factor that effects your army size is in fact the starving time that you wish to have. For example, in a purely hypothetical situation whereby you have a 30 minute starving time, therefore are able to have a 224650 negative crop in each city, you are able to have a total army that consume up to 1,528,860 crop an hour. This means you could have around 150k cats. However on the other extreme, if you do not wish to have a starve time, then your armies capacity is severely reduced.
On a final note, lets consider a level 20, with enhancements, lv 20 crop in every city, level 10 planting tech, and level 9 crop oasis, with a 5 hour starve (which I have seen many players manage).
This would mean that they would be able to maintain an army consuming up to 337,380 crop an hour, without starving. However with the 5 hour starve, you are able to add around 89,000 per city. As they have 7 cities that they control, they are able to maintain an army that can consume up to 960,380 crop an hour. This is how some players have the huge armies that you see that have over 200k cav, or over 70-80k cats.
I hope you can find this useful, and if you have any questions please don't be afraid to ask.