Corn, which has been trading near its lowest in six months, was also nearly flat, with investors reluctant to take big positions ahead of a US Agriculture Department supply-demand report on Friday.
"South American crop expectations are keeping a lid on soybean prices," said Ker Chung Yang, senior investment analyst at Phillip Futures in Singapore. "It is also some positioning before the USDA report, which will shed light on South American production, as well as give the final number on last year's US output."
Chicago Board of Trade March soybeans eased 1-1/4 cents to $13.87-1/4 a bushel by 0353 GMT, after having climbed 1.4 percent in the last session on technical buying.
CBOT March wheat rose 0.4 percent to $7.54 a bushel, while March corn added 0.2 percent to $6.87 a bushel.
Technical signals are very mixed for the March soybeans contract as it is not clear how strong the support at $13.56 is and how long soybeans could hover above this level, Reuters technical analyst Wang Tao said.
The support is jointly provided by the Nov. 16 low and the 76.4 percent Fibonacci projection level of the wave c, which started at the Jan. 2 high of $14.35.
But March wheat is expected to break a resistance at $7.59 and rebound further to $7.71 per bushel.
Friday's USDA report will give the final update on 2012 US crop production. Trading has been particularly volatile following the January supply-and-demand report, with corn making limit moves on the day of the release six times in a row.
Agricultural analyst Clarivi lowered its estimate for Brazil's 2012/13 corn crop by 2 percent, but raised its forecast for the soybean crop slightly, saying farmers favoured planting the oilseed this season.
Clarivi expects 72.06 million tonnes of corn from Brazil, down from its 73.57-million-tonne forecast in December. The firm raised its forecast for soy slightly, to 83.11 million tonnes from 83 million previously.
Dry weather is expected in Argentina for the next seven days followed by some light rain, said John Dee, a meteorologist for Global Weather Monitoring.
Investors are keeping a watch on demand outlook in China, the world's top importer, which has cancelled US cargoes in the last few weeks on an improved supply outlook in rival exporter Brazil.
In the US cash market, corn spot basis bids were steady to higher across the US Midwest on Monday as futures touched their lowest since July, chilling the already lackluster selling interest from farmers.
Commodity funds bought a net 6,000 CBOT corn contracts on Monday, trade sources said. They bought 1,000 wheat and bought 7,000 soybeans.
