Chicago Board of Trade corn futures fell on Wednesday, retreating from early gains on technical selling, traders said. The benchmark CBOT March corn futures contract turned lower after failing to hold support above its 20-day moving average for the third day in a row.

It also fell below its 10-day moving average. Declines were kept in check by concerns that dry weather in Argentina could keep yields from that key South American producer in check.

Private analytics firm IEG Vantage, formerly known as Informa Economics IEG, on Wednesday forecast Argentina's 2019/20 corn production at 46 million tonnes, according to an IEG client note seen by Reuters. The US Agriculture Department's latest report had pegged the crop at 50 million tonnes.

Analysts were expecting a USDA report on Thursday morning to show that weekly export sales of corn were between 500,000 tonnes and 900,000 tonnes. That compares with 806,751 tonnes a week earlier.