What version of the game do you have?

Raw production contributes directly to the base social manufacturing, ship manufacturing, research, and income of each planet.  You should try to maximize the raw production by increasing your population, building asteroid mines, and upgrading your capitals.  At least in Retribution (and I think back to Crusade) putting your space elevator next to your colony capital gives an adjacency bonus to the capital that raises raw production by +1.  And don't forget those asteroid mines.

As for planets like Mars, they really can only become productive after you've researched the terraforming type techs that you can use to add tiles to it.

i agree with the original post, and publius. First you build 4 factories, or hub buildings. Then you build farms, but you can only build enough farming to not exceed the class if the planet.

Maybe it was added for Retribution?

I also would like to place colony capitals when colonising a planet.