spade, shovel, marking pin
鍤 centers on a digging or piercing tool: a spade or shovel used for earth, and by extension a marking pin that is inserted into the ground.
鍤 combines 金 (metal) with 臿, which likely contributes the sound and is associated with a tool for digging or piercing. The exact historical development of 臿 is uncertain.
The left side 金 (metal) and the right side 臿 (which looks like a tool with a long handle and a blade) together suggest a metal digging tool: a spade or shovel. The marking pin sense comes from the idea of piercing the ground with a metal spike.
For ソウ, imagine using a spade to sow seeds: sow -> ソウ, and the metal spade digs the furrow.