Between 1815 and 1846 the price paid for grain grown by British farmers was protected from foreign competition by tariffs charged for all imported grain (which was cheaper) under what were called "The Corn Laws".
Aerial photography of the kind you can find on Google Earth is a wonderful tool to show where grain (oats, barley and wheat) were grown on land in Northumberland which went back to pasture and low fertility grazing after 1846. The "rig and furrow" contour is the telltale sign of this arable farming at elevations which today would not be considered suitable.
Regular ploughing with a pair of horses pulling a single furrow plough made the rig and furrow contour. Ploughing started by "setting out" to plough a "land".
On grassland (lea) you first ploughed a very shallow furrow in one direction just scraping off the grass and exposing the soil. Then you turned the horses around and cut a similar shallow furrow next to the first back in the opposite direction. This was "opening up".
The next task was to throw these two opened furrows together to complete the set-out which made sure that there was no grass left growing under the set-out to poke its way up through.
Ploughing then continued round and around this set-out in a clockwise direction (called gathering) until it became too inconvenient to run the plough empty along the "headland" as this involved a bit of physical effort by using your weight on the plough handles to keep the coulter out of the ground.
At this stage another new setout was started about 7 yards away and this was gathered until it became too far to run empty on the headland.
Then the land left between each setout was ploughed in an anticlockwise direction (called throwing out) so the plough had very little distance to travel empty on the headland.
The final job was to organise the "finish" so that one final furrow width was left to be turned over with the last passage of the plough so no land was left unploughed.
After years of this practice, the setouts got higher and the finishes got deeper resulting in very clear rigs (ridges) and furrows still visible today from satellites and on the ground when walking across them. On heavy clay land, a major advantage of rigs and furrows was to provide good, simple and low cost surface drainage.
The other advantage was that when sowing the grain by hand, you could walk up the open finish which was much easier on your feet and legs throwing grain to either side which would reach the top of the ridge. It's very hard on your ankles to walk all day on the tops of ploughed furrows.
Rigs and furrows were not always ploughed in a straight line; they were sometimes made in sweeping curves and always across and not up and down the sides of hills. At the Northumberland Farm Institute at Kirkley Hall in 1951 the rigs and furrows in the front parks were so deep after many decades of ploughing, that you could not see resting sheep in the bottom of the furrow from a distance across the field. At lambing time you had to check every furrow.
When these parks were ploughed with tractor and mounted plough, they had to be ploughed so the set out was in the furrow and the finish on the ridge top to try to level the contour. I well remember the tractor driver being very frustrated at all the extra work involved, and his Northumbrian adjectives to describe those who created the historic contours. It took a few years to get a reasonably level surface on the fields.