spade up, plow
鋤 centers on turning over soil with a tool: spading up earth or plowing a field.
鋤 combines 金 (metal) with 助, which likely contributes the sound and the idea of assisting or helping, suggesting a metal tool that helps with working the soil.
The left side is metal 金, and the right side is 助 (help). Picture a metal spade helping you turn the earth.
For ジョ, imagine a farmer named Joe who loves to plow: Joe -> ジョ, and his metal spade helps him spade up the field.
spade
plow (esp. horse or ox-drawn); plough
Chinese "Three Stars" constellation (one of the 28 mansions)
to turn over soil; to dig or plow up (plough)
to plow (up); to plough (up)
to plough; to plow; to hoe; to till
(long-handled) bamboo winnow used to sift earth or sand
spadefoot toad (Pelobatidae spp.)
farming implement
vomer (bone of the skull)
vomeronasal organ
removing snow (e.g. from a roof)
seafood and vegetables cooked sukiyaki style and served with udon