You do not need to submerge much stem. Winding the rest of the stem around the soil surface could result in most nodes taking root & growing new vines. I've found that although cuttings will root right in soil, they have an easier time if put in water for a couple weeks first, until a white, elongated root starts to grow on one of the nodes from which I've removed leaves to be submerged. Usually the last 2-3 nodes of a cutting. Once you get that root going, submerge it and wind the rest around the surface. Use small rocks or other means to keep the vines in contact with the soil surface so those other nodes can take root and grow new vines. That should yield much more new plant mass vs. chopping a same piece into more cuttings.
