CHICAGO (Reuters) -A crop data blackout during the longest-ever U.S. government shutdown has led to the widest range of analyst estimates in a decade for corn and soybean yields, as an information vacuum at harvest time and during critical trade negotiations distorted the market for the country's two most valuable crops.

On Friday, the U.S. Department of Agriculture is set to release a hotly anticipated crop report including the government's first estimates of the two feed crops since mid-September, before the harvest had taken shape. In the absence of last month's world agriculture supply and demand estimates report, traders have relied on disparate bits of data to take positions.

Buyers and analysts have examined harvest estimates from private forecasters, media reports about export sales, local cash market prices, and social media posts showing overflowing grain bins in some parts of the country and ample storage space in others. None of this, however, gives as definitive a picture as the USDA report.

"It's at harvest, when we are trying to figure out the true size of the crops. It's the worst time to be without that information because it robs the market of essential production data," said Scott Irwin, a University of Illinois agricultural economist.

Analysts' highest and lowest corn crop estimates reflect a difference of 389 million bushels of production, more than Michigan's entire crop last year. Their soybean estimates reflect a difference of opinion equal to 184 million bushels, half of Indiana's crop in 2024.

The government's crucial export sales data remains suspended, fueling uncertainty about crop demand during the busiest period of the year for shipments, leaving markets reliant on rumors of trade negotiation breakthroughs or the threats of new tariffs. 

On October 30, Treasury Secretary Scott Bessent said China had agreed to purchase 12 million tons by December. The main U.S. soybean buyer has shunned U.S. supplies during President Donald Trump's trade war. Beijing has not yet confirmed a deal and trade sources told Reuters that China has booked rival South American supplies in recent days with only minimal purchases from the U.S.

Markets remain on edge, raising stakes for farmers and traders ahead of Friday's USDA report. Pre-report estimates gathered from analysts and brokers showed exceptionally varied opinions.

Estimates for average 2025 U.S. corn yields ranged from 181.7 to 186.0 bushels per acre -- all below USDA's September estimate of 186.7. Estimates for U.S. soybean stocks remaining ahead of the next harvest were between 187 million and 494 million bushels, a spread nearly three times as wide as normal. 

In September, USDA projected the largest corn and soybean yields on record and the largest harvested area for corn since the Great Depression. But in the absence of updated government data, analyst consensus has been building that the two crops' harvest will come in smaller than projected.

Analysts with farm lender CoBank warned of an acute crop storage shortage, but grain piles never materialized in many areas. In October, buyers in some locations began bidding up the cash price for crops, reinforcing ideas that the harvest had fallen short.

The USDA's last supply-demand report was released on September 12, as the U.S. corn and soy harvests were just beginning. Both are now nearly complete, according to private analysts regularly polled by Reuters during the shutdown. Aside from anecdotal farmer reports, it was unclear how badly late-season dryness and crop disease impacted national production. 

The USDA told Reuters that its staff collected crop field samples despite the shutdown. Lance Honig, an official with the USDA's National Agricultural Statistics Service, said the statistical methodology for estimating national yields had not changed and the agency was "collecting the necessary survey and administrative data to support the forecasts."

EXPORT UNCERTAINTY

The USDA also suspended crop export sales reporting during the shutdown, although it was still gathering the data, according to its shutdown plan. In past shutdowns, the agency has released missing data once the government reopens.

But the current blackout coincided with trade negotiations with China, which accounts for 50% to 60% of all U.S. soybean exports. The U.S. ships about two-thirds of the oilseed, its most valuable farm export, between October and January.

Buyers other than China have booked U.S. soybean shipments during the shutdown. But without weekly government confirmation of sales, estimates of demand have varied significantly.

Analysts surveyed by Reuters during the data blackout estimated net soybean sales of between 3 million and 102 million tons over six weeks. Sales as of the end of October may be down 50% from a year ago at the lowest since 2007, or down merely 25% at the lowest since the last U.S.-China trade war in 2019.