PARIS/SINGAPORE: Chicago corn futures eased for a fourth consecutive session on Thursday as favourable crop weather in the US Midwest reinforced the prospect of a big harvest this year.

Soybeans also ticked lower, curbed by the crop-friendly Midwest weather, while wheat steadied after recent losses linked to an advancing US winter wheat harvest.

Investors concerns about rising coronavirus outbreaks worldwide leading to fresh lockdown measures kept a check on grains as they did in other commodity markets.

Grain traders were also awaiting weekly US export sales data at 1230 GMT for a demand update while starting to look ahead to US government planting estimates next Tuesday.

The most-active corn contract on the Chicago Board Of Trade (CBOT) was down 0.3% at $3.23-1/4 a bushel by 1051 GMT, close to a three-week low touched on Tuesday.

Forecasts for showers and moderate heat across the Midwest have eased worries about crop stress after a recent dry spell.

"With a bumper 400 million tonnes of US corn crop coming our way, it is hard to build a bullish argument for corn," said Ole Houe, director of advisory services at agriculture brokerage IKON Commodities in Sydney.

CBOT soybeans edged down 0.3% to $8.67-3/4 a bushel. CBOT wheat added 0.3% to $4.87 a bushel but remained near a nine-month low struck last Friday.

Soybeans were capped by weaker vegetable oil and crude oil prices, as well as uncertainty over US-Chinese relations that was tempering optimism about recent Chinese purchases of US soy.

Wheat markets remained under pressure from improving prospects for northern hemisphere production, with an advancing US winter wheat harvest showing some better than expected yields and analysts raising forecasts for Russia's crop.

"The wheat market is currently experiencing the classic harvesting pressure now that around a third of the US winter wheat crop has been harvested," Commerzbank said.