Most farmland that has been abandoned (at least in the US) has been abandoned due to some other imposed restriction (usually water, but in some more marginal la

Most farmland that has been abandoned (at least in the US) has been abandoned due to some other imposed restriction (usually water, but in some more marginal land, it could be fertilizer or pesticide). Having a new use for soya isn't going to move that needle -- but if construction will pay more for soya than food manufacturers will for whatever the most-marginal current crop is, some currently-available food crop will go to road building instead.