The typical Roman recruit did not need to be taught to farm, he was a farmer. Well into the Principate the military levy was still primarily done in the countryside, and rural young men were preferred as recruits as late as Vegetius. Only two urban levies stand out in my memory, Marius' emergency levy during the Jugurthine War and Augustus' after the Teutoburg disaster. There are surely others that I can't think of off the top of my head, but the point is clear: in both cases urban levies were conducted due to a perceived shortage of available manpower, and armies only turned to urban recruits generally when rural manpower had run dry. The image of the Marsian farmboy, muscled and conditioned to the elements from working on his father's plot in the Apennines, continued to be the stereotypical image of the Roman soldier long after recruitment had passed out of Italy and into the provinces--Lavan finds that after military recruitment had almost entirely left Italy, recruits were still almost exclusively rural.

"Land grants" rarely occurred for soldiers until the Principate. When they did, it was typically in colonies, where soldiers would have had their own plots, but also a centralized urban center for the veterans. So Capua during Caesar's consulship, and Carthage, Corinth, and the various Augustan veteran colonies later. Saturninus settled Marius' veterans on plots in the Ager Gallicus, Sulla settled his, but such things were not common. Typical Republican land distributions did not target veterans, but the citizen body at large: thus Flaminius' distribution of the ager publicus in 232, Ti. Gracchus' land commission in 133, C. Gracchus' abortive attempt to set up a colony at Carthage, and so forth. The case of Sulla's veterans is particularly noteworthy. Sulla's veterans appear by 63 to have largely failed in their attempt to become (or, probably more accurately, return to being) farmers. They seem to have run up large debts--always a major threat for the premodern farmer, at the mercy of the harvest with no Green Revolution buffer to help him out--and largely sold off their plots, becoming a major part of Manlius' revolt. The problem is that it's somewhat uncertain why. Other veteran settlements went off without problems, and there seems to be nothing particularly unusual about the Sullan veterans. By all rights they should have been no less successful than the Marians to the north, the Caesarian and Augustan veterans in the provinces, and Pompey's veterans, who were settled in the vicinity of Capua. It's been suggested that perhaps the land that they were on was not great, and the centuriations of the distribution might have resulted in wildly uneven quality. Recently I've seen the suggestion that there was a brief climate crisis in the Mediterranean and part of central Europe between the 100s and 60s or 50s, but that would suggest that Pompey's troops and the several citizen land distributions of the period should have seen similar problems, and they are simply not singled out in our sources. The opinion of the ancient authors is simply that Sulla's veterans were lazy vultures, who had enlisted to reap profit from the plunder of the Mithridatic war but who had no interest in or knowledge of real work. This sort of moralistic explanation need occupy little of our time. The only other thing of this sort is a series of comments by Cicero in the de lege agraria on the undesirability of farming. Cicero, attempting to combat an agrarian bill that would place too much power in the hands of political enemies, at one point argues that compared to the advantages of the city, farming is hard work, and work that his audience has no idea about. But Cicero is addressing an urban citizen crowd at a contio in the forum, precisely the sort of people who he might expect did know nothing about farming. This is not the typical recruitment pool of the army.

It's worth mentioning that the Gracchan land commission rendered some small aid to farmers entering their plots. Ti. Gracchus, in what Stockton shows was the real beef the senate had with him, rather abruptly passed a plebiscite that earmarked the proceeds of the fortune of Attalus for the purchase of farming equipment and seed, to be distributed to the recipients of public land distributions--this, in violation of the usual custom, that placed public funds in the hands of senatorially-appointed magistrates. We do not know whether distributing such aid was standard practice during land distributions, and we have little reason to believe that it was so. Nonetheless, by far the majority of the Roman army, until quite late, would have known at least the basics of farming already, because it would have occupied their entire pre-military life.