mane
騣 centers on the long hair along a horse's neck: the mane.
騣 combines 馬 (horse) with 㚇, which likely contributes the sound and may relate to hair or bristles, forming a character for a horse's mane.
The left side is a horse 馬, and the right side 㚇 looks like a bristly crest. Picture a horse with a flowing mane standing tall.
For ソウ, imagine a horse's mane blowing in the wind as it sows seeds across a field: sow -> ソウ, and the mane flows like the scattered seeds.