Martell: Rain Needed Across Corn Belt

May 21, 2012 04:03 AM

The following content was provided by meteorologist Gail Martell of

Too Much Heat, Not Enough Rain in U.S. Corn Belt

Temperatures have been incredibly warm in the U.S. heartland over the past 30 days with not enough rainfall to compensate. Field moisture is declining over a widening swath of the grain belt. As a general rule, Midwest field moisture is abundant in the spring, as soil profiles are recharged from winter rain and snowmelt. This year, conditions are dry.

Low Rainfall Past 2 Weeks

The drier weather pattern this spring has allowed for rapid planting of corn and soybeans, but the downside has been a steady decline in field moisture. Dryness has developed in a wide swath from the Central Great Plains into Missouri, Illinois and Indiana and including the Mid South.

Nebraska is the driest of the major U.S. corn states on May 13 reporting 32% short-very short field moisture. Illinois and Indiana have reported 18% and 15% deficient topsoil moisture, respectively. The percentage of dry soil conditions is expected to rise on the May 20 report from USDA. Though weekend showers produced locally heavy rainfall, only 30% of the U.S. Corn Belt has received significant rain, over .75 inch.

Persistent heat is reducing the effectiveness of showers, keeping evaporation elevated. The rate of evaporation increases sharply above 80 F. This makes it hard for rainfall to keep up to crop moisture needs. There have been 16 days over 80 F in Omaha, Nebraska and 12 days over 90 F in Champaign, Illinois, in the recent 30 days.


Kernel Shriveling From Kansas Heat Stress

Kansas wheat is in a state of rapid decline from heat and moisture stress. Conditions May 13 from USDA were 52% good-excellent, 32% fair and 16% poor-very poor. One month earlier, crop ratings were sharply higher at 69% good-excellent, 24% fair and 7% poor-very poor April 15. This was very rapid deterioration in wheat potential in the grain-filling stage.

5 dayrainfall outlook

Kansas wheat production was pegged at 387 million bushels in the first official crop production report , valid May 1. At this level the Kansas harvest would be the 7th largest in 20 years and 40% bigger than last season when a devastating drought occurred. Production is apt to decline in subsequent reports from USDA, reflecting kernel shriveling from heat and moisture stress.

Weather Rather Like La Nina

Pronounced heat is associated with the La Nina. It has continued despite La Nina weakening April through May. In fact the Climate Prediction Center has pronounced the La Nina official dead in early May, claiming that ENSO-neutral conditions were in effect. This would mean neither La Nina nor El Nino is in effect. Presumably, with neutral conditions La Nina weather (hot and dry) would alternate with El Nino (cool and rainy).

Presently, weather conditions resemble La Nina more than El Nino. The new forecast is still hot over the majority of the grain belt this week. Rainfall would be light, once again, over the majority of the corn belt. Indeed the only states expecting generous rain would be Minnesota and North and South Dakota. If this forecast verifies, field moisture would continue to decline.




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