Multi-furrow wheelless plough

An innovation of the traditional single-furrow wheeled plough, the wheelless plough made a great impact due to requiring far less effort to pull. The design was quickly expanded into one featuring three sets of plough-blades, allowing three furrows to be pulled at the same time, in about the same effort as older ploughs would take for a single furrow.
The multi-plough had a great impact on the old country, as it helped turn far larger areas of land into usable farmland. With most land being uneven, saving time and effort turned farming from a survival thing to actually profitable. Additionally, multi-furrows meant less area wasted due to crooked lines. What once was an area of famine, was turned into an area of commerce.
It might seem over-the-top, but it is no exaggeration to say that without the multi-plough, the old country might never have turned independent. Without the improved farming, there would have been no food or money to raise an army. Only the mines would have been able to earn money, and the nobles owning those would have still faced food supply shortages.
So no multi-plough, no becoming independence. No independence, no old country. No old country, no new war. No new war, no destroyed dam. And no destroyed dam, no fleeing to the valley. So without that plough, not only would we have far lower numbers, we never would have been here in freedom, but back there in chains. That is even ignoring how useful these ploughs are in establishing new farmlands in the valley.
That said, there is a weakness to the plough. It requires a significant amount of solid steel, which slowly deteriorates in use. As steel is currently in short supply, and hard to re-use without a dedicated forge, we may run out of our steel supplies soon. Yet another possible shortage to keep an eye on.