The U. S. Agriculture Department, or USDA, zigged on Monday when the market expected it to zag.

The farming agency released its monthly world grain report, called WASDE, and, surprisingly, the agency sees a bigger U. S. corn crop—despite poor weather in the Midwest. Corn prices cratered as a result.

Corn futures contact prices dropped “limit down” on Monday—dropping about 6%—meaning futures reached their maximum allowable daily losses on Chicago exchanges. And corn prices were down again Tuesday. What roiled commodity traders was the USDA increasing the expected corn yield per acre for farmers in the 2018/2019 crop year. (For farmers the “crop year” goes from harvest to harvest. ) The USDA now expect farmers to produce about 169 bushels of corn per acre, up from expecting 166 in July. (Bad weather has had an impact though—U. S. corn yield was more than 176 bushels per acre last year. )

That’s good news if you are a user of corn, such as a food company, such as corn buyer Post (ticker: POST).

“We view the USDA’s August WASDE report as positive for packaged food manufacturers, as fears over a run-up in grain-driven input cost inflation are being alleviated by a robust corn supply outlook, ” writes Citigroup analyst Cornell Burnette in a Tuesday research report. “Thus, our positive thesis for the sector remains intact. ”

But higher corn production isn’t such good news if you sell inputs or equipment to farmers, such as Deere (DE).

“Deere’s near-term fundamentals were challenging exiting the second quarter 2019 but there was hope that investors could look through near-term weakness as higher corn prices would deliver demand reacceleration in 2020, ” writes Baird analyst Mig Dobre in a Monday evening research report. “The 2019 crop still has challenges that could drive prices higher, but the near term is decidedly more difficult after today’s USDA forecast updates. ” Dobre rates shares of Deere Buy, but he cut his price target to $150 from $170 based on the USDA news.

Things could still change for the U. S. corn outlook. Weather, exports, ethanol demand all feed into the USDA models, and all inputs are fluid. Agricultural consultant Mark Feight of International Agribusiness Group, or IAG, believes the corn acreage figures could still come down when the USDA reports figures in October.

Stocks usually don’t overreact to a single crop report because equity prices reflect long-term business value—at least, that’s what the theory says. The long-term trend in agricultural prices and acreage matters more for stocks. Still, there were some big moves along the agricultural value chain on Monday.

Post, for instance, dropped 1.4% on Monday along with the 400-point drop of the Dow Jones Industrial Average. That wasn’t a surprise, but ethanol producer Green Plains (GPRE) actually dropped 4.3%, even though corn is an input for the company. Ethanol demand also influences Green Plains stock. Input provider Corteva (CTVA) dropped 6%, and tractor maker Deere dropped 5% in Monday trading.