The farmer reaping hay or grain would have to stop work in the field when the scythe gets dull. They stop several times per hour, throughout the day, for sharpening. That would often be done using a whetstone -- a cut piece of naturally abrasive stone that is used to hone the edge.
Here is Farmer Wayne peening the scythe blade in the blacksmith's shop.
This peening is done on a scythe anvil. This is a small, portable anvil that can be driven into the top of a stump or fencepost and be used in the field. These were used by farmers in many countries. The name for them in German is a “denglestock”, because the little anvil dangles from the farmer’s belt on a cord.