SustenanceThese are the spells I removed from the Change Environment category:
Purify Food & Water 
Make poisoned and/or spoiled food & water safe to consume. Affects enough to feed up to 12 men.
Create Water 
Creates enough water for 12 men and their mounts. The quantity doubles for every caster level above 8.
Create Food 
Creates enough water for 12 men. The quantity doubles for every caster level above 8.
MechanicsThe only anomaly is the fact that Create Water specifically mentions mounts whereas Create Food does not. Interestingly, this is corrected in B/X. I will follow suit and assume Create Food also creates enough for mounts as well. Additionally, since some of the potential spells will be less than forth level, I am going to change the "doubles for every caster level above 8" to "+ caster level x2." This will approximate the same effect while allowing it to span across a wider range of caster levels.
Base spell: 1st level. Purify poisoned/spoiled food and water enough for 12 men.
The following add one spell level:
- Quantity adds (caster level x2) men.
- Quantity adds mounts.
- Substitute "create water" for "purify poisoned/spoiled food and water."
The following add two spell levels:
- Substitute "create food" for "purify poisoned/spoiled food and water."
4th level spell. Create food (+2 levels) enough for 12 + (caster level x2) men (+1 level).