WASHINGTON — The preliminary national average price received by farmers for all wheat in May was $6.60 per bu, down 51c from $7.11 in April and down $1.56 from $8.16 in May 2011, the U.S. Department of Agriculture said in its latest Agricultural Prices report.

The average price paid for winter wheat in May was $6.18 per bu, down 29c from $6.47 in April and down $1.62 from $7.80 in May 2011. The average price paid for durum was $8.75 a bu, down 43c from $9.18 in April but up 89c from $7.86 a year earlier. Spring wheat other than durum averaged $7.61 a bu, down 34c from $7.95 in April and down $1.24 from $8.85 in May 2011.

The average price paid for all rice was $13.70 a cwt, down 20c from $13.90 in April but up $1 from $12.70 in May 2011.

The May index of prices received by farmers for food grains was 216 compared with the 1990-1992 base of 100, down 4% from 226 the previous month and down 15% from 253 in May 2011.

The May index of feed grains was 269, down 1% from 272 in April but up 1% from 266 in May 2011. The average price paid to farmers for corn was $6.22 a bu, down 12c from $6.34 in April and down 10c from $6.32 in May 2011. Farmers received an average of $10.10 a cwt from grain sorghum in April, down 50c from $10.60 in April and down $1.50 from $11.60 in May 2011.

The average price paid for oats in May was $3.76 a bu, down 5c from $3.81 in April but up 21c from $3.55 in May 2011.

The index of May prices received for oilseeds was 245, unchanged from April but up 3% from 237 in May 2011. Farmers received an average of $13.70 a bu for soybeans in May, unchanged from April but up 50c from $13.20 in May 2011.

The May index for dairy products was 126, down 2% from 129 in April and down 16% from 150 in May 2011. The average price for all milk in May was $16.40 a cwt, down 40c from $16.80 in April and down $3.20 from $19.60 in May 2011.

The May poultry and egg index was 163, up 3% from 159 in April and up 5% from 155 in May 2011. The average price paid to farmers for all eggs in May was 83c, down 3c from 86c in April and up 1c from 82c in May 2011.