Varro, Rerum Rusticarum de Agri Cultura 1. 17
“All fields are cultivated by men—by slaves, freemen, or both; by freemen, either when they farm themselves as many poor people do with their own families, or as hired hands when the more serious parts of the work are done by contracting with freeman, such as the pressing of the vines or the haying, or by use of those our people used to call obaerarii [debtors], of whom now there are still many in Asia, Egypt, and Illyria.
In general, this is what I say about these groups: it is more effective to work the harsher places with paid workers than with slaves—even in more hospitable areas too this is the case for the heavier agricultural work , as in warehousing the harvest or the new wine. Concerning the nature of these men, Cassius writes this: that workers should be selected who are capable of carrying out the labor, who are no less than twenty-two years old, and who have some preparation for agricultural work. It is possible to evaluate this from other tasks they have been assigned or, in the case of considering new hires, by asking what sorts of things they used to do for their previous boss.”
Omnes agri coluntur hominibus servis aut liberis aut utrisque: liberis, aut cum ipsi colunt, ut plerique pauperculi cum sua progenie, aut mercennariis, cum conducticiis liberorum operis res maiores, ut vindemias ac faenisicia, administrant, iique quos obaerarios nostri vocitarunt et etiam nunc sunt in Asia atque Aegypto et in Illyrico complures. De quibus universis hoc dico, gravia loca utilius esse mercennariis colere quam servis, et in salubribus quoque locis opera rustica maiora, ut sunt in condendis fructibus vindemiae aut messis. De iis, cuius modi esse oporteat, Cassius scribit haec: operarios parandos esse, qui laborem ferre possint, ne minores annorum XXII et ad agri culturam dociles. Eam coniecturam fieri posse ex aliarum rerum imperatis, et in eo eorum e noviciis requisitione, ad priorem dominum quid factitarint.