Ag Weather Forum

Dryness Hurts Missouri Yields

Bryce Anderson
By  Bryce Anderson , DTN Senior Ag Meteorologist
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Strange as it seems, parts of Missouri which had record-breaking rain in spring and early summer now have moderate drought in effect. (NDMC graphic)

What a difference a year makes. At this time in 2014, Missouri farmers were well on their way to a corn crop that averaged 186.0 bushels per acre, and a soybean harvest of 46.5 bushels per acre. This year, corn yield is down to 149.0 bushels per acre in USDA's October 9 production estimate, with soybeans pegged at 41.0 bushels per acre. Missouri's corn production is now estimated at 469.4 million bushels, 25 percent below a year ago, with soybeans at 189.4 million bushels, down 27 percent from 2014.

Some of that yield and production loss is due to incredibly heavy rain and flooding. The state's harvested corn acreage is 230,000 acres less than 2014, and the soybean harvested acreage number is close to one million acres less than a year ago--down 970,000 acres. That's a total of 1.2 Million acres that did not get planted in 2015. It's by far the greatest acreage loss from the spring-to-early summer flooding in the Midwest.

But, another factor that compromised yield performance--and makes this 2015 season a real head-scratcher--is that, peculiar though it may be, late-season dryness developed and took the edge off yields. (Yes, the term "flash drought" applies.)

The following summary is from the Missouri Extension Service:

"COLUMBIA, Mo. -- Rain needed in September and August to boost corn and soybean yields this year didn't happen, worsening a growing season fraught with weather woes.

Four weather stations in Missouri's soybean-producing areas report less than a third of the normal September precipitation, says Bill Wiebold, University of Missouri Extension agronomist. A fifth station, in Gentry County, showed a single 3-inch rain before rain shut off, leaving northwestern Missouri as dry as the rest of the state.

Normal rainfall might have repaired some damage to late-planted soybean. Usually, September rainfall has minimal effect on soybean yield, except for double-cropped.

A significant amount of acres were planted after July 1 because of a historically wet spring, Wiebold says.

Delayed planting shifted the most critical stage for soybean water need from the first two weeks of August to the first two weeks of September, Wiebold says.

'Farmers who planted soybean in July understood their crop was at risk,' he says. 'But the degree of drought in August and September was highly unusual and impossible to predict.'

For good to excellent soybean yields, plants need about 1.2 inches of rain each week during grain fill. In most of Missouri, monthly average rainfall in August and September is 4 inches, which would have helped greatly this year, Wiebold says.

Claypan fields in northeastern Missouri, which were drenched by heavy rains this spring, are especially hard hit. Claypan soils restrict water drainage and reduce root depth during the growing season, making the region especially vulnerable to drought stress.

Producers report reasonably high soybean yields so far, Wiebold says, but these yields come from fields planted in a timely manner.

Soybean harvest season continues for longer than normal this year because of the wide range of planting dates. Soybean harvested in mid-to-late October will be from fields most affected by the lack of rain in late summer and fall."

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