Soybeans were up 0.6 percent to $14.45 a bushel and wheat added 0.3 percent at $6.55-1/2 a bushel.
The US Department of Agriculture said the US corn crop was 8 percent planted, matching the five-year average but just behind the average estimate in a Reuters analyst poll for 9 percent.
Sub-freezing temperatures are expected across most of the Plains and the Midwest this week along with some snow and rain. Meanwhile, dry conditions persist in the northern Plains.
The USDA said soybean planting was 3 percent complete, ahead of the five-year average of 2 percent and in line with trade expectations.
The USDA rated 53 percent of the US winter wheat crop in good to excellent condition, unchanged from the previous week. Analysts on average had expected a decline of one percentage point.
Brazil has suspended import duties on soy, corn, soybean meal and soybean oil until the end of the year, the Agriculture Ministry said on Monday, as the country seeks to slow inflation fanned by rising global commodities prices.
Commodity funds were net buyers of CBOT corn, soybean and soymeal futures contracts on Monday and net sellers of soyoil and wheat futures, traders said.
