Well, that depends. The farm is a complicated thing, and can be affected by many different factors resulting from game play styles. I won't divulge all of the inner workings of the farm here, but I can offer some general tips:

Changing game speed and pausing the game for long periods of time, to name two things, can influence the crop cycles in ways that create stress for the person holding the stylus.

Also, in general, it's a bad idea to switch from a slower game speed to a faster game speed while the farm is empty. And, finally, if your peeps are ever in a food crisis before you have fishing, switching the game back to slow speed until the crops appear can help the villagers survive.