U.S. grain and soybean futures fell on Friday amid profit-taking by traders following advances notched earlier in the week. Wheat prices fell to a three-week low as traders booked profits ahead of the weekend after prices climbed in previous sessions. Analysts said traders were discouraged from holding long positions in the wheat market after the USDA projected stockpiles of the grain would swell because of poor demand for U.S. supplies. The USDA on Friday said wheat reserves will likely rise 10% to 763 mil bu in the 2015-16 crop year, which would be the highest level in 5 years. Prices also were pressured by a weekly report showing slower export sales of the crop, with sales for the 2014-15 crop year down 35% in the week ended Feb. 12 from the previous week and 41% from the previous four-week average.