CHICAGO, May 21 (UPI) -- Grain futures prices closed lower Friday on the Chicago Board of Trade. Corn was fractionally lower on forecasts for beneficial growing weather next week and losses in the wheat pits. Good export sales limited losses. Soybeans were lower on a disappointing weekly NOPA crush figure of 26.896 million bushels, down 3.167 million from last week. Beneficial weather forecasts added pressure. Wheat closed lower with contracts hitting new lows on heavy supplies and slow exports. At the close, corn was off 1/2 to off 3/4; soybeans were off 5 1/2 to off 6 1/4; wheat was off 1 3/4 to off 4 3/4; oats were off 3/4 to off 1 3/4.  