This morning, I've been out raking a freshly spaded row to plant some sorghum in. Since our CSA uses tillage and mulch to control weeds, we are left with only the weeds that survive tillage and mulch. While the uncultivated sections of land in the corners of our property are growing a plethora of wild plants, the cultivated rows are growing little more than creeping grasses and purslane: the only stuff that is killed by neither tillage nor deep mulch. With no other weeds capable of surviving this double whammy and coming back to contend with the creepers, those little bastards run rampant like a caffeinated 5 year old on an airplane.
The way I see it, there are 3 options. The first being to go Full Polyanna and convince yourself that the virtues of crab grass outweigh the cons (even as everything you plant among the grass shrivels up like an 90 year old penis). The second would be to break out the "bigger hammer", till twice and use more mulch. The third, and by far the most practical, would be to reintroduce those tillage fearing plants that my colleagues have dilligently driven to extinction by sowing a cover crop after harvest rather than letting the crab grass reclaim the row.
By sowing a cover crop, you introduce vegetation that will compete with the crab grass but not with your all mighty spade. Will it miraculously eliminate crab grass in one season? I suspect not, but it will certaintly decrease those noxious, creeping stems with less human labor than anything else, barring and act of God, that I can imagine.