John Deere shares slide on questions over how long farm boom can last

John Deere tractors are seen for sale at a dealer in Longmont, Colorado, U.S.. REUTERS/Rick Wilking/File Photo

Michael Hirtzer

Deere & Co. shares slipped Friday as investors questioned how much longer the boom in sales of tractors and other farm machinery can last amid slumping crop prices.

The world's top agricultural equipment producer lifted its profit outlook for the year and its third-quarter earnings results surpassed analyst estimates, according to a statement Friday. Still, farmers are likely to slow machinery purchases as soon as grain markets normalize. Deere shares fell as much as 5.5%, the most since April.