In the Gudersnipe Foundation
A move was made early on in the Foundation's history to get away from traditional farming techniques, to avoid heavy reliance on crops grown in the ground, which itself created sanitation issues, required careful land managment, and on the whole left the food supply to the fickle whims of nature.
In the early Third Age, crops were grown hydroponically indoors, negating the need for traditional methods. Growing food in soild eventually became known as "dirt farming" or "growing things in the dirt"; but this knowledge was felt vital to preserve, and reserve farms were established. The primary goal of these organizations was education; students from schools took field trips, and citizens were encouraged to understand it.
The reserve farms are not responsible for the food supply, but rather a living knowledge-base for preservation of farming techniques: in the event of cataclysm, some people will still know how to make things grow. They provide less than 5% of the total food supply, and recieve grants from the Foundation to ensure their continued survival even when crops fail.
Reserve farms are often family-owned and generational, some having existed for thousands of years. They are small and sometimes specialize in a specific crop.
Before the shift to hydroponics, the Foundation experimented with farm worlds, in which entire planets were devoted to growing crops.
In the Unity Earth Sphere Alliance
The Alliance allows each member nation to provide for itself along whatever lines it deems fit. This can include dirt-farming, hydroponics, interplanetary trade, synthetic cultivation, and almost anything else (except robbery).