4, at $3 billion; hay, which is mostly alfalfa, comes in at No. 8, with $1.6 billion in receipts. Growing hay and other forage and irrigating pasture for livestock (mainly cattle) takes at least ...

In industrialized nations, hay fever—also known as allergic rhinitis ... the number of people allergic to ragweed could grow from 33 million to 77 million, as the plant spreads into new areas.