Martell: Midwest Drought Intensifies

July 30, 2012 03:32 AM

Meteorologist Gail Martell of has provided the following weekly highlights:

Worsening Corn Damage From Intense Heat and Drought

Sizzling hot temperatures occurred again last week in the United States heartland. July temperatures may turn out to be the hottest since 1955, based on preliminary data.

5 week drought Corn Belt

A large, stable dome of high pressure has taken up residence in the Central United States, causing the intense heat wave. Extreme heat has been present for 5 consecutive weeks, coinciding with the critical pollination period in corn. Damage to the corn yield will be irreversible, since kernels not successfully fertilized would never develop into grain.

July 2012 Extreme Heat

Drought has intensified in a large bloc of corn states with the persistent dome of high pressure. Included were the top 4 United States corn states Iowa, Illinois, Nebraska and Minnesota, along with Missouri, Kansas, South Dakota and Wisconsin. The heat dome has dealt a devastating blow to United States corn prospects, expanding west of the Mississippi River in July, where the majority of United States corn is grown.

Earlier in the growing season, corn in the Eastern Midwest corn fell victim to intense drought in Indiana, Illinois, Wisconsin and Ohio. Corn condition by July 22 had fallen to only 11% good-excellent, 26% fair and 63% poor-very poor, as a weighted average based on production. These 4 states grow 32% of United States corn.

Iowa, the leading U.S. corn state, has received only 1.75 inches of rainfall the past 5 weeks and 48% of normal. July temperatures have averaged 78.8 F and 5.4 F above normal, threatening the July record for extreme heat in 1955 and 79.1 degrees F.

The combination of intense heat and drought in Iowa has led to a severe decline in corn. Good-excellent corn in the state fell to only 23% on July 22, compared to 68% good-excellent four weeks earlier. The poor-very poor corn increased to 40% up from just 8% four weeks prior.

Crop ratings are expected to decline across the board in Midwest growing areas in the July 29 USDA report, due out this afternoon.

Rare Drought Argues for Severe Yield Damage

Drought this intense is a rare occurrence in the Midwest Corn Belt. The last instance of such swift decline in corn occurred in 1988. The ’88 summer drought began easing after mid July, suggesting slight improvement may have occurred late in the growing season. Corn losses, nonetheless, were extreme in 1988, the national yield still finishing 23-24% below trend. More than 5% of the crop was abandoned, either cut for silage or left in the field as a total loss.

Crop watchers last week predicted a national corn yield of 130-132 bushels per acre, and 18-19% below trend. Another yield reduction may be justified from intense drought and heat stress, perhaps down another 2-3 bushels to 128-129 bushels per acre. Corn was already 86% pollinated July 22 and 22% denting, the fastest development on record. This is a manifestation of extreme heat and drought stress.

Gail Martell Coming up mid morning, a look at the updated Midwest weather forecast. Conditions this week will remain very hot and dry. The Omaha, Nebraska, maximum temperatures, Monday through Friday are projected at 95F, 97F, 96F, 94F and 96F. There is a 20% chance for showers Wednesday and Thursday. Peoria, Illinois highs this week would be 93 F, 94F, 91F, 93F, and 91F with no rain in the forecast.







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