A stalk is the standing stem of a plant or grain. It may also mean a cane or piece of wood, depending on the underlying word. In agricultural imagery, a stalk represents the result of a sowing.
The expression “they sow the wind” is explained as a worthless sowing that produces no stalk and therefore no grain. The image emphasizes the failure of an empty or destructive activity to yield a harvest.
The word translates several terms meaning cane, wood, or that which stands. The Revised Version’s “standing grain” in some passages may obscure the figurative contrast between sowing and the absence of a stalk.