WASHINGTON — The preliminary national average price received by farmers for all wheat in May was $8.19 per bu, up 15c from $8.04 in April and up $3.86 from $4.33 in May 2010, the U.S. Department of Agriculture said in its latest Agricultural Prices report.

The average price paid for winter wheat in May was $7.70 a bu, up 31c from $7.39 in April and up $3.49 from $4.21 in May 2010. The average price paid for durum was $8.44 a bu, down 16c from $8.60 in April but up $4.16 from $4.28 in May 2010. Spring wheat other than durum averaged $9.20 per bu, up 53c from $8.67 in April and up $4.59 from $4.61 in May 2010.

The average price paid for rough rice in May was $13.40 a cwt, up 40c from $13 in April but down 40c from $13.80 a year ago.

The May index of prices received for food grains was 256 compared with the 1990-92 base of 100, up 4.5% from 245 the previous month and up 62% from 158 in May 2010.

The May index for feed grains was 259, down 1.1% from 262 the previous month but up 70% from 152 in May 2010. The average price paid to farmers for corn was $6.15 a bu, down 20c from $6.35 in April but up $2.67 from $3.48 in May 2010. Farmers received an average of $10.80 a cwt for grain sorghum in May, down 90c from $11.70 in April but up $5.11 from $5.69 in May 2010. The average price paid for oats in May was $3.49 a bu, down 4c from $3.53 in April but up $1.30 from $2.19 in May 2010.

The index of May prices received for oilseeds was 233, down 1% from 235 in April but up 39% from 168 in May 2010. Farmers received an average of $13 a bu for soybeans in May, down 10c from $13.10 in April but up $3.59 from $9.41 in May 2010.

The May index for dairy products was 149, down 1% from 150 in April but up 30% from 115 in May 2010. The average price for all milk was $20.50 a cwt, down 70c from $21.20 in April but up $4.70 from $15.80 a year ago.

The May poultry and egg index was 155, down 2% from 158 in April but up 3% from 150 in May 2010. The average price paid to farmers for all eggs in May was $1.05 a dozen, down 4c from $1.09 in April but up 25c from 80c in May 2010.