Fair weather is speeding the US corn and soybean harvests, of which more than 14m acres were harvested in a week, but has held farmers back from planting winter wheat.

US growers had harvested 26% of their corn crop as of Sunday, a record pace by this time of year, and above the 24% figure that investors had expected, US Department of Agriculture showed.

It also represented an 11-point increase in a week – equivalent to approaching 10m acres in area and nearly 1.2bn bushels (93m tonnes) of crop by weight.

Besides dry weather, the early harvest of the world's biggest corn crop beyond an average rate of 9% by now is also being speeded by early plantings and – excessively - rapid development fostered in many areas by summer drought.

'Earliest harvest I have observed'

The harvest is particularly advanced in Missouri, where two-thirds of the crop has been harvested compared with less than one-quarter typically by now.

"There have been a few reports of [Iowa] farmers completing corn harvest," the officials noted, adding that one of their scouts had reported that "this is the earliest harvest I have observed in my career".

The condition of the US crop improved two points to 24% rated good or excellent, although traders urged caution in reading too much into this figure, as better crops were likely to be those harvested later, needing a longer time to develop.

'Increased the pace'

For soybeans, the harvest also set a record pace, of 10% complete, up six points on both the week and the average pace.

Growers in North Dakota, where "dry conditions last week pushed maturity of standing crops and increased the pace of harvest", were particularly ahead of their typical harvest pace.

And this week is expected to see more rapid progress in row crop harvests.

"The weather outlook features minimal rain this week so it's expected that harvest should continue at a good rate," Brian Henry at broker Benson Quinn Commodities said.

Harvest pressure

The speed of the harvests, coupled with some recent reports of better-than-expected yields, has been seen by investors as a major factor in Monday's tumble in crop prices, bringing a spike in supplies and therefore more options for buyers, for now.

"Fundamentals are strong, but seasonals are lower," Mike Mawdsley at broker Market 1 said.

"This is the time of year that pressure is normally seen until harvest is more advance."

The rapid development of the crops is also seen as protecting them from early frosts.

"The only state threatened by frost the next two mornings is Wisconsin, where only 40% corn  is mature versus 80% and 93% in North Dakota and Minnesota respectively," Richard Feltes at RJ O'Brien said.

'Wheat seeding was slow'

However, the dry weather was also reflected in a pace of winter wheat sowings which, at 11% complete, lagged the typical figure of 14% by now.

"Winter wheat seeding was slow with emergence limited due to dry topsoils," USDA staff said.

In Colorado, a hard red winter wheat state, where "conditions are still very dry", the pace of sowings also lagged significantly behind the average.

One-way bet?

In Texas, some farmers were "aided by cooler temperatures and timely rains".

But "in places that missed last week's rains, dry planting was underway, with growers sowing into dry soils, in hope of rains, and with insurance programmes promising decent payouts for failed crops.

"The insurance for hard red winter wheat came in at $8.78 a bushel, which will get winter wheat planted," Mr Henry said.