WASHINGTON — The condition of the corn crop as of July 21 in the 18 main corn-growing states declined three percentage points from a week earlier in the good to excellent categories, the U.S. Department of Agriculture said in its most recent Crop Progress report.

As of July 21, a total of 63% of the crop was rated good to excellent, down from 66% the previous week. A total of 11% was rated very poor to poor in the latest week, compared with 9% the previous week, the U.S.D.A. said. Despite the decline, the crop fared far better than a year ago when good to excellent ratings were only 26% and poor to very poor ratings were 45%.

Corn development advanced rapidly in the most recent week, the U.S.D.A. said, with 43% of the crop in the silking stage, up from 16% the previous week and compared with 56% as the five-year average for the date.

The weekly decline in the condition rating was about what was expected by the trade, but corn futures were down sharply early July 23 due to improved rainfall in parts of the Corn Belt. The rainfall would be occurring during the key pollination stage.

The soybean crop also advanced rapidly but still lagged the five-year average for some growth benchmarks. The U.S.D.A. said 46% of the crop was blooming in the 18 main soybean-growing states, up from 26% as of July 14 but below the five-year average of 59%. A total of 8% of the crop was setting pods as of July 21, behind the five-year average of 19%, the U.S.D.A. said.

Soybean conditions were rated 64% good to excellent, down slightly from 65% a week earlier but well above 31% a year ago. The crop was rated 8% poor to very poor, the same as a week earlier but far better than 35% a year ago.

The winter wheat harvest as of July 21 had virtually caught up with the five-year average for the date. The U.S.D.A. said 75% of the crop in the 18 main winter-wheat states was harvested compared with 76% as the five-year average.

The U.S.D.A. said 85% of the spring wheat crop was headed in the six main spring wheat states, down from the 88% five-year average but up from 71% in the previous week. Crop condition declined slightly in the latest week to 68% good to excellent, compared with 70% in the previous week.

The oats harvest in the nine main oats-growing states advanced by six percentage points from the previous week but still lagged the five-year average. The U.S.D.A. said 18% of the crop was harvested as of July 21, down from the 26% five-year average.

The condition of the rice crop in the six main rice-growing states improved modestly in the latest week, with 72% of the crop rated good to excellent compared with 68% the previous week, the U.S.D.A. said. A total of 24% of the rice crop was headed as of July 21, up from 13% the previous week but down from a five-year average of 32%.