The next USDA monthly supply/demand update, due out on Tuesday morning, is expected to show lower U.S. corn, soybean and wheat ending stocks for 2011-12 and lower South American soybean production.

Trade estimates of the 2011-12 U.S. corn carryout average 717 million bushels in a range from 626-801 million bushels, compared with USDA’s current estimate of 801 million and last year’s carryout of 1.128 billion bushels, according to a survey of 16 analysts by Dow Jones Newswires.

Pre-report expectations for soybean ending stocks average 246 million bushels in a range from 225-275 million bushels compared with USDA’s current estimate of 275 million bushels and last year’s 215-million-bushel carryout.

Trade forecasts for wheat ending stocks average 796 million bushels in a range from 740-825 million compared with USDA’s current estimate of 825 million bushels and last year’s carryout of 862 million.

Corn stocks are expected to be lowered based on a lower-than-expected March 1 wheat stocks estimate, which implied higher feed/residual usage than USDA is currently estimating. March 1 corn stocks came in at 6.010 billion bushels compared with trade estimates averaging 6.155 billion.

Corn export sales have fallen behind pace to meet USDA’s current export target, however, so exports could be lowered by 50 million bushels, partly offsetting any increase in feed/residual use.

The soybean carryout is expected to be lowered due to prospects for larger U.S. exports because of South American crop losses.

On average, the trade expects USDA to cut combined production for Argentina and Brazil by 2.7 million metric tons from its March estimate of 95 million tons.

Estimates of Brazilian soybean production from 13 analysts surveyed by Dow Jones Newswires average 67 million tons compared with USDA’s March estimate of 68.5 million. Estimates of Argentine production average 45.3 million tons versus USDA’s March estimate of 46.5 million.

However, U.S. export sales are still running well behind the pace needed to meet USDA’s current export forecast, so the department may again hold off raising that forecast. Export sales are about 21.6% behind a year earlier, with USDA forecasting a 15% drop in marketing year exports.

The wheat carryout is also expected to be cut because of a lower-than-expected March 1 wheat stocks total that implied higher-than-expected wheat feed/residual use. March 1 wheat stocks came in at 1.200 billion bushels compared with trade estimates averaging 1.233 billion bushels.