WASHINGTON — Corn and soybean development remained behind average, crop ratings declined from recent hot, dry weather, and the soybean market traded higher as forecasts called for continued limited rainfall.

Corn in the 18 major states was 4% mature as of Sept. 1, compared with 38% at the same time last year and 17% as the 2008-12 average for the date, the U.S. Department of Agriculture said in its Sept. 3 Crop Progress report. The crop was 84% in dough stage, catching up with 89% as the five-year average.

The corn crop was rated 56% good to excellent, down from 59% a week earlier but well above 22% at the same time last year. Sixteen per cent of the crop was rated poor to very poor (14% a week earlier and 52% a year ago), with 28% rated fair (27% a week ago, 26% last year.)

The 18-state aggregate soybean crop condition was rated 54% good to excellent, down from 58% a week earlier but well above 30% a year ago, with 31% fair (29% and 33%, respectively) and 15% poor to very poor (13% and 37%), according to the U.S.D.A.

Ninety-two per cent of the soybean crop was setting pods, slightly below 96% as the five-year average and 98% a year ago, the U.S.D.A. said.

The trade generally was more concerned about the soybean crop because of hot, dry weather during the key yield-determining pod setting and filling stages. Soybean futures traded at the CME Group rose to six-week highs Monday after disappointing weekend rainfall and a forecast of mostly dry weather across the Corn Belt the next few days. Corn futures, meanwhile, traded slightly lower Monday, except in spot September.

Pressure on new crop corn came from declining cash basis levels and active corn harvest in southern states that was moving northward.

While the hot, dry weather was detrimental to fall row crops, it aided farmers who were harvesting spring wheat. Harvest in the six key states jumped to 64% completed as of Sept. 1, up from 42% a week earlier and slightly behind 69% as the 2008-12 average, which was in part boosted by last year’s early crop that was 93% harvested by the same date. Spring wheat condition in the six states was rated 70% good to excellent, up from 67% a week earlier.