The S.M.I. is set by ministerial order for each county, within the master plan for agricultural structures prepared and set by the Prefect, after advice from the General Council, the Chamber of Agriculture and the County Commission for Agricultural Direction. It is revised periodically.
It is set for each county by zone (e.g. plain zone or so-called underprivileged zone) and is weighted according to the type of crops (S.M.I. different depending on the crop: pasture, land suitable for mechanical farming, vines, trees, etc.). Non-land production S.M.I. are national (the same in every county).
Example of S.M.I
In the county of Vienne, the S.M.I is 25 ha for the plain zone and 34 ha for the “underprivileged” zone.