Q: I would very much like to be able to "mow" my field with a scythe. But in all the videos and pictures I see of people using a scythe, the ground appears quite even. My ground is quite bumpy, and the grass (fescue, I think it is) grows in clumps. Would a scythe work on such a field? Would a shorter blade work better?
A: Yes, you can use a scythe on uneven ground having clumps of grass. (Most of my backyard could be described this way.)
However, the irregular surface will make it easier for the blade tip to dig into the ground, or for the heel of the blade to dip into a low spot, so more attention will have to be given to the horizontal control of the blade. This usually translates to a firmer grip, less width of the swath, and occasionally some slight "hovering" of the blade above irregularities.
For such terrain, Peter Vido advises that the blade should not be longer than 70cm. For a beginner, 60cm is probably sufficient. If the mowing is mainly "trimming" of smaller areas, an even shorter blade can be used.
If you have a sizeable open grassy area (with uneven ground and clumps of grass) and you want to make hay, then a relatively stiff 70cm blade is recommended (like blade #9 in ScytheConnection's catalogue). A shorter blade is easier for beginners, but will cut less grass with each stroke, requiring more time to do the job.
If you instead will be walking from clump to clump to cut them individually, then a blade as short as 40 or 45cm should be sufficient.
(Source: Photo of "A field in Vesper, Oregon" copyright 2009 by Halvorsen brian,