US farmers received a warning over the threat of dryness to 2013 crops even as a dearth of rain helped a record-fast harvesting campaign of crops which, in soybeans' case, are showing a late revival in condition.

Growers harvested 13% of their corn last week to get 39% of their crop in silos as of Sunday, three times the proportion they have normally reaped by now, US Department of Agriculture data showed.

For soybeans too, the harvest progressed at a record pace, reaching 22% complete, up 12 points over the week, and ahead of the typical figure of 12% of the crop in the barn at this time of year.

The progress reflected, besides early crop development speeded by early sowings and in some cases drought stress, dry conditions which allowed field work to continue largely unimpeded.

Iowa, the top corn and soybean producing state, "experienced little rain during the week resulting in ideal harvest conditions for farmers," USDA officials said, noting that a few farmers completed their corn harvests.

In second-ranked Illinois, "cool, dry weather across much of the state allowed for producers to continue their rapid pace for corn and soybean harvest," USDA scouts said.

'Perpetuates a very serious drought'

However, the dryness is provoking too the threat of this year's drought conditions extending to affect 2013 crops too, crop weather expert Gail Martell at Martell Crop Projections.

"North-central US is extremely dry in key corn states Iowa, Nebraska and Minnesota. Surrounding farmland also is exceptionally dry in northern Illinois, Wisconsin, Missouri, and eastern parts of South and North Dakota.

"To put this into perspective, Iowa would need 50% above-normal rainfall in the seven months October through April to completely restore field moisture for spring planting in 2013."

Wheat sowings lag

Indeed, dry weather has been blamed in part for a slight lag in winter wheat sowings behind the average pace, reaching 25% complete as of Sunday, two points below the typical figure for this time of year, even though many farmers are taking a chance on planting into dry soils.

In Nebraska, where plantings were running 12 points behind the average pace "winter wheat seeding was nearing the half-way point but fields were slow to emerge due to dry soil conditions".

Rabobank analysts said 40% of area earmarked for US hard red winter wheat plantings received less than 50% of average rainfall in the month to September 20, posing "a risk to the establishment of the crop".

'First widespread, hard freeze'

Nonetheless, the crop progress data showed another threat to crops, from the first frosts of the 2012-13 winter, failing to register crop damage.

Indeed, in South Dakota, which witnessed the "first widespread, hard freeze to the north eastern part of the state", soybeans improved by two points over the week to 27% in "good" or "excellent" health.

In neighbouring North Dakota, where "widespread frost occurred in many areas last week", the proportion of soybeans in good or excellent health jumped seven points to 60%.

Further south, Ohio soybeans also enjoyed a seven-point recovery, but amid "cool, damp weather", which also slowed harvesting activity.

The overall US soybean crop improved by two points in good or excellent categories to 35%, its highest in 11 weeks.