Chicago wheat inched higher as wet weather was similarly seen hampering sowing of spring wheat, while soybeans ticked lower, partly pressured by the possibility that setbacks in corn planting will shift some area towards the oilseed.
A steadying in the dollar, after a pause in a euro rally that followed Sunday's first round of France's presidential election, curbed US grain prices.
The most active corn contract at the Chicago Board Of Trade rose 0.3 percent to $3.72-3/4 a bushel by 1037 GMT. It had gained 1.7 percent in the previous session when prices hit a high of $3.74-3/4 a bushel - their highest since March 8.
Analysts said corn continues to draw support from fears of further planting delays, with forecasts for rainy weather and colder temperatures into early May likely to keep corn planting behind the average pace.
"It is too wet to plant and with prices perhaps not as attractive, further delays could encourage farmers to switch to soybeans," said Phin Ziebell, agribusiness economist, at the National Australia Bank.
The US Department of Agriculture estimated US corn planting at 17 percent complete as of Sunday, well behind last season's pace of 28 percent and slightly below the five-year average of 18 percent.
Weather risks to US spring planting have helped underpin corn, which has been pressured in recent months from large global supplies that are set to be swelled further by bumper South American harvests.
The most active CBOT wheat futures rose 0.3 percent to $4.28-1/4 a bushel, having closed up nearly 2 percent on Tuesday, while soybeans fell 0.2 percent to $9.63-1/2 a bushel, adding to a 0.7 percent decline on Tuesday.
Wheat has found technical support after spot prices reached the psychological $4 floor this week, while wet weather has also put spring wheat sowing below the average pace of recent years.
Soybeans, however, have faced some pressure from the idea that US farmers could add more acres of soybeans, which can be planted later than corn, if soggy conditions prevent some corn plantings.
In Europe, rapeseed futures edged higher, supported by concern that frosts since last week could damage crops in the flowering stage.
"European rapeseed is the most penalized by the current cold conditions with fears in France, but also in Germany and Romania," consultancy Agritel said in a note.