* Soy up from last session's drop to weakest since Dec 2020
* Market awaits key crop supply-demand reports Thursday
* Focus on South American corn and soybean crop estimates
CHICAGO, Feb 6 (Reuters) - U.S. soybean futures firmed on Tuesday for a second straight session as short-covering and technical-buying fueled a bounce from multi-year lows a day earlier, though concerns about weak demand limited gains.
Wheat futures also rose, while corn ended lower on forecasts for rain in Argentina, where hot and dry conditions have been stressing the crop.
Traders also squared positions ahead of two key crop reports on Thursday from the U.S. Department of Agriculture (USDA) and Brazil's Conab, with a keen focus on crop production updates for Brazil and Argentina.
Brazilian farmers have sown 27% of the area expected to be planted with second corn in the center-south, marking the fastest pace for second corn planting since records began in 2013, agribusiness consultancy AgRural said on Monday.
"The trade is doing a little bottom-picking in beans ... The trade estimates indicate that we could see a contraction in soybeans and corn for Brazil in the reports," said Terry Reilly, senior agricultural strategist with Marex.
Analysts polled by Reuters, on average, also expect the USDA to slightly increase its corn and soy harvest forecasts for Argentina.
Chicago Board of Trade (CBOT) March soybeans were 3-1/4 cents higher at $11.99-1/2 per bushel after touching the lowest level for a most-active contract since December 2020 on Monday.
March corn was down 4 cents at $4.38-3/4 a bushel, while CBOT March wheat rose 4-3/4 cents to $5.95 a bushel.
Statistics Canada is also scheduled to release estimates of Canadian crop stocks as of Dec. 31 on Thursday. (Additional reporting by Naveen Thukral in Singapore and Sybille de La Hamaide in Paris; Editing by Rashmi Aich, Subhranshu Sahu, Krishna Chandra Eluri, Andrea Ricci and David Gregorio)
