Incidence of Force sensitively in the Old Republic

If I recall, the series of books chronicalling Obi-Wan's youth, suggested that younglings not taken as padawans by their 13th birthday were shipped to the agricultural corps. That doesn't make much sense, as Andle says above, without the full Jedi Training (both Anakin and Luke being prime examples) it's much easier for the person to go over to the Dark Side, mainly through lack of emotional control rather than mastery of the Force, and if there is a whole agricultural core of half-trained Jedi who are none to happy with their lot in life, they'd probably be more than capable of starting another civil war.
I can just see the title... StarWars Episode X: Return of the Farmers