WASHINGTON — The preliminary national average price received by farmers for all wheat in May was $4.39 per bu, down 3c from April and down $1.45 from $5.84 in May 2009, the U.S. Department of Agriculture said in its latest Agriculture Prices report.

The average price paid for winter wheat in May was $4.10 a bu, down 9c from April and down $1.42 from $5.52 in May 2009. The average paid for durum was $4.27 a bu, up 4c from April but down $2.78 from $7.05 in May 2009. Spring wheat other than durum averaged $5.04 a bu in May, up 15c from $4.89 in April but down $1.72 from $6.76 in May 2009.

The average paid for rough rice was $14.10 a cwt, up 30c from $13.80 in April but down 50c from $14.60 in May 2009.

The May index of prices received for food grains was 160 compared with the 1990-92 base of 100, down 1.8% from a revised 163 in April and down 20% from 199 a year earlier.

The May index for feed grains was 149, up about 1% from a revised 148 last month and down 14% from 173 in May 2009. The average price received for corn in May was $3.41 per bu, unchanged from April but down 55c from $3.96 in May 2009. Farmers received an average of $5.31 a cwt for grain sorghum in May, down 8c from April and down 67c from $5.98 in May 2009. The average price paid for oats in May was $2.04 a bu, down 21c from $2.25 in April and down 60c from $2.64 in May of the previous year.

The U.S.D.A. index of May prices received for oil-bearing crops was 165, down 2.4% from 169 in April and down 14% from 191 in May 2009. The national average price paid to farmers for soybeans was $9.28 a bu, down 19c from $9.47 in April and down $1.42 in May 2009.

The May index for dairy products was 115, up 2.7% from 112 in April and up 29% from 89 in May 2009. The average price paid for manufacturing grade milk in May was $13.50 a cwt, up 20c from April and up $2.90 from $10.60 in May 2009.

The egg and poultry index was 147, up 2.1% from a revised 144 in April and up 3.5% from 142 in May 2009. The average price paid to farmers for all eggs was 63c a dozen, down 14c from 77c in April but up about 1c from May 2009.