More on Soil Temperatures in Illinois

Here are the average dates in fall when the 4-inch soil temperature falls below 50 degrees (left panel) and below 60 degrees (right panel). Consider these as a “rule of thumb” for planning purposes. Consult the current soil temperatures, as discussed in the earlier post, for decisions on applying nitrogen in the fall.

Average date when 4-inch soil temperature drops below 50 and 60 degrees.
Average date in fall when the 4-inch soil temperature drops a) below 50 degrees, and b) below 60 degrees.


Daily Soil Temperatures Across Illinois

The Illinois State Water Survey operates a network of 19 sites that report daily soil temperatures at 4 and 8 inches.
Soil temperatures in the fall are critical for the application of nitrogen (N) fertilizer. According to the Agronomy Handbook (University of Illinois), “fall N applications should be done when daily maximum bare soil temperature at 4 inches is below 50 degrees.”
The daily maximum and minimum soil temperatures are measured over grass. In addition, the values are adjusted using regression to estimate the bare soil temperatures, to better represent the soil temperatures in a cultivated field. Grass tends to insulate the soil so the daily temperature swing is a little smaller than over bare ground. In addition,  soil temperatures within a particular field may vary due to soil color, soil moisture, and crop residue on the surface.
You can see the daily data and maps at

Better Weather for Pumpkins in Illinois

I have to admit – I am a big fan of pumpkin pie. So I was concerned about the news stories about the pumpkin shortage. It turns out that Illinois is home to 95 percent of pumpkin production used for pie filling. In fact, Morton, in central Illinois, is considered the pumpkin capital of the world.
Last year was terrible for pumpkin production around Morton. After a wet growing season, October rains that were 3 times the average, over already wet fields, prevented growers from harvesting most of the 2009 crop.
Conditions in 2010 around Morton have been better so far. After a wet start, conditions in July and August were much drier. And the NWS forecast for October is for increased odds of warmer and drier than normal weather. Here’s to a successful pumpkin harvest.

Monthly Rainfall Totals (inches) for Morton, IL for this year, last year, and average (1998-2008).
Month 2010 2009 Average
April 3.8″ 7.3″ 3.8″
May 6.2″ 5.7″ 4.9″
June 6.8″ 5.1″ 4.0″
July 3.8″ 3.1″ 3.9″
August 2.0″ 4.5″ 3.2″
September 1.7″ 2.6″ 2.9″
October 8.9″ 2.9″

**the total for September, 2010, is through the 17th.

Impact of Wet Fields on Corn

Emerson Nafziger, University of Illinois agronomist, posted an interesting article about the impact of wet fields on newly planted corn. The article appears in the current issue of The Bulletin, published by the College of Agricultural, Consumer, and Environmental Sciences (ACES).  The article starts out about frost damage but halfway down Emerson addresses the potential damage of all the heavy rains.

A larger concern after heavy rainfall in parts of Illinois this week will be standing water and, for the crop recently planted, the possibility of emergence problems. There were a few reports of death of germinating seeds in fields planted a few days before heavy rain in parts of western and southwestern Illinois, but this is not widespread. We think that such seeds simply ran out of oxygen and that shoots died before emergence. Seedlings that have emerged and have roots are more resilient, but there is a very good chance that plants that stand in water for more than two or three days will not survive, especially if temperatures go up. Higher temperatures mean less oxygen in the water and also faster seedling metabolism rates, so plants run out of oxygen sooner.
Even if plants survive, their regrowth can be slow due to poor conditions around the roots. Diseases can also invade plants that stand in water; one example is the downy mildew fungus that can carry crazy-top, whose symptoms won’t appear for weeks after the water is gone. In any case, we often see plant size and health diminish as we move from the edge to the middle of low areas where water stood. If the size of the drowned-out area is large enough to justify a repair-planting after it dries up, it might be a good idea to plant into the area around the edge with living but slow-growing plants as well, in order to replace sickly plants with healthy ones.

In an earlier post, I noted that areas in western and northern Illinois were exceptionally wet in the first half of May. The latest NASS report for Illinois shows that as of May 16, 56 percent of the state had topsoil moisture rated as surplus.

Cool, Wet Start to May

The first half of May was both cool and wet. Preliminary data indicates that statewide temperatures were 1.4 °F below normal for the period May 1-17. Meanwhile, precipitation has been abundant. The statewide average precipitation was 4.15 inches, 1.79 inches above normal or 176 percent of normal. The heaviest rains have fallen in western and northern Illinois. The largest month-to-date total reported was 8.24 inches in Dallas City (along the Mississippi River between Quincy and Moline) by a CoCoRaHS observer.

Table 1. Precipitation totals by climate division in Illinois, along with the 1971-2000 normals, and percent of normal, for May 1-17, 2009.
Climate Region Precipitation (in) Normal (in) Departure (percent)
Northwest 4.64 2.25 206
Northeast 4.55 2.06 221
West 5.84 2.46 238
Central 4.17 2.32 179
East 3.17 2.21 143
South Southwest 4.26 2.43 175
South Southeast 3.67 2.46 149
Southwest 3.37 2.49 135
Southeast 3.51 2.66 132
State 4.15 2.36 176

Illinois was surrounded on three sides by very wet conditions in parts of Missouri, Iowa, Wisconsin, as well as Kentucky. The rains in Illinois have produced saturated soils in places and minor to moderate flooding along the Mississippi and Illinois Rivers and their tributaries.

May 1-16 precipitation
Precipitation totals for the Midwest for the period May 1-16, 2010 (click to enlarge).

May 1-16 percent of normal precipitation
Percent of normal precipitation across the Midwest for May 1-16, 2010 (click to enlarge).

Warm Start to April

April is off to a warm start with statewide temperatures 10.0 degrees above normal for the first 18 days of April. The statewide average precipitation is 1.66 inches, 76 percent of average. The warmer-than-normal temperatures were prevalent throughout the eastern two-thirds of US but were most intense in the Midwest and Northeast.
The combination of warm temperature, strong winds, and low humidity have aided in drying out fields. According to the National Agriculture Statistics Service, near the beginning of the month 50 percent of the fields in Illinois were rated with surplus moisture. By the April 19 report, this number had dropped to 7 percent.

US Temperature Departure, April 1-19, 2010.
US Temperature Departure, April 1-19, 2010 (click to enlarge).