The topic of Agricultural Urbanism is fascinating to me and like many tenets of the New Urbanism movement, there is something very intrinsic about how agriculture relates to urbanism.
There may be confusion in what Agricultural Urbanism is compared to Urban Agriculture.  Andres Duany, Author of an upcoming book on Agrarian Urbanism and co-founder of the Congress for the New Urbanism, provides the following definition to assist in understanding the difference between Agricultural Urbanism and Urban Agriculture.

“Agricultural urbanism creates a walkable urban form surrounded by large-scale food production, while urban agriculture simply refers to growing food in empty lots or backyards.” – Andres Duany

Both Agricultural Urbanism and Urban Agriculture have similar intentions, that is to provide something closer to independence in regards to food.  Society today in the United States (and most other non-Third World countries) are very dependent on others in providing food.  Specifically, society is dependent on oil as a means of transporting and gathering food from grocers, who import the majority of the food from across the country or outside of the United States.
I believe that Agricultural Urbanism can easily be applied to many of the “entitled” Planned-Unit Developments across the United States.  “The New Economy” has provided many opportunities where this can be incorporated.  For example, a square mile (640 acres) of land entitled for 5-acre single-family lots could arguably be “clustered” as 2-1/2 acre lots under common conventional county zoning codes.  By clustering the homes and using smaller lot sizes, there is an opportunity for 240 smaller lots on the 640 acre parcel of land.  Using an approximate net density of 6 dwelling units/acre, 240 detached single-family lots can be achieved on only 40 acres of land, preserving the remaining 600 acres for agricultural use.

A transfer of development rights provide for more compact development accomplishing two times the density on 1/16th of the land. This abstract diagram shows a square mile of 5-acre lots in the northeast quadrant and smaller lots at a net density of 6 dwelling units per acre on the other adjacent quadrants of the intersection. The remaining land is preserved for agricultural uses. In an ideal situation, the crops produced from the adjacent agricultural uses would be shared by the residents through a cooperative agreement.

This application of a “transfer of development rights,” or TDR, allows for compact development that is more cost-effective for the developer, less intrusive on the land, and provides for decreased stormwater runoff.  The long term maintenance costs for the county is also decreased with less infrastructure to be maintained.
If this concept were applied on all four corners of 4 square miles (2,560 acres), an agricultural-based village could be a reality with a small urban footprint of 160 acres and approximately 2,400 acres of agricultural land.