1)Growth: Each population represents 10,000 people. When you look at the city manager, it tells you the pop growth rate per turn. Divide 10,000 by this number to figure the number of turns to a new pop.

2)Farms: the effect of tile improvements depend on the percentage of resources being collected in the radius ring in which the improvement is placed. I think most of us have figured that out. What many people are having trouble with is why growth rate sometimes drops so much when a city grows.
Part of the answer is that, when a city grows, happiness usually decreases by one percent, and crime increases by one percent. This crime raise affects all food production, and this cumulative effect all comes out of the surplus, thus sometimes having a significant effect on growth.

Thanks for that bit of info, but having an additional line of type with the actual turns to the next pop. growth would of been nice too, and would of been more practical.

A city that started with pop=29950 and a growth rate of +600, happiness=74, crime=20%, then grew to pop=30530 with a growth rate now of only +400, with happiness=74 and crime=20%. For comparison sake, I raised wages at this point and happiness went up to 76 and crime fell to 18%, but the growth only grew to +450.