Skip Navigation

8/8/2011 - 8/14/2011

CREP Wetland Tour near Nashua Aug. 24

By John Lundvall, Iowa Learning Farms

Iowa Learning Farms (ILF) and the Iowa Department of Agriculture and Land Stewardship (IDALS) are hosting a tour of a Conservation Reserve Enhancement Program (CREP) wetland near Nashua in southeast Floyd County on Wednesday, Aug. 24, starting at 5:30 p.m.

The CREP wetland tour will be held in conjunction with the 2011 Iowa Drainage School at the Borlaug Learning Center on the Iowa State University Northeast Research and Demonstration Farm near Nashua. The tour will depart from and return to the Borlaug Learning Center. The tour is free and will include a complimentary evening meal. The public is invited to register for the tour (separate from the Iowa Drainage School). To register, please phone 515-294-5429, or email:

Tour participants are encouraged to bring their hiking boots or waders for an up-close look at the CREP wetland structure. Matt Lechtenberg and Shawn Richmond, CREP specialists with IDALS, and Iowa State University Extension water quality engineer Matt Helmers will lead the tour and talk about the benefits, installation and financial incentives for these structures. 

There are 37 counties in north-central Iowa eligible for enrollment in CREP. Research at Iowa State University has demonstrated that strategically sited and designed wetlands can remove 40-90 percent of nitrates and over 70 percent of herbicides from cropland drainage waters. These areas are as beautiful as they are functional. Tour participants are welcome to bring their hiking boots or waders to see these structures up close.

The research farm is located at 3321 290th Street, Nashua; take exit 220 off Hwy 218 and travel 1.2 miles west on county road B-60 (280th Street). Go 1 mile south on Windfall Avenue, then 0.2 mile east on 290th Street. The Borlaug Learning Center and farm headquarters are located on the north side of the road.


John Lundvall is the Iowa Learning Farms field coordinator. He can be reached at 515-294-8912 or by emailing

August 2011 Iowa Corn Yield Forecast

Roger Elmore and Elwynn Taylor, Department of Agronomy

USDA released the first corn yield forecast for 2011 on Aug. 11. Forecast U.S. yields of 153 bushels per acre are similar to last years' and six bushels below the 30-year trend line (Figure 1). This is not surprising. 

On the other hand, Iowa’s forecast of 177 bushels per acre matches that of the 30-year trend line and lies 12 bushels above last year’s final yield estimate. This, if realized, would rank third highest behind 2004 (181) and 2009 (182) bushels per acre for Iowa. This seems unlikely.

Pollination issues like those shown in the recent ICM article, Weather Impact on Midwest Corn 2011, are just part of the problem. The other issue is kernel weight reduction that will likely occur because of the high night temperatures during pollination which resulted in rapid crop development. This sounds like a replay of 2010, at least for Iowa corn.

Remember these forecasts arise from meticulous late-July counts and measurements by the team at USDA-NASS and that each forecast is a “new” forecast – not simply an update. USDA-NASS use new and expanded observations from a large number of sample locations to formulate expected yields based on field observations for every subsequent Crop Report. They assume that weather during the remainder of the grain filling season is normal. The September yield forecast is likely to be lower than the one just issued because ear size will be less than the average ear size. Later, when the forecast includes kernel counts the yield forecasts  will again change. 

Of course, it is possible that the weather could be better than average for crop yield and actually increase the yield forecast in subsequent months. This is usually associated with temperatures that extend the filling period beyond normal. Don’t forget that when acres are dropped from the harvested area – due to flooding, etc.,  “yield” increases simply because “yield” means “yield per harvested acre.”

Earlier this week USDA-NASS reported that about two-thirds of Iowa’s corn was in or past the milk stage. At dent, the crop needs about a month of growing season to finish well. Kernels contain less than half of their final weight at dent. Much can change in a month.

Figure 1.  Corn yields over 30 years for Iowa and U.S. Trendline (tl) yields are shown in the open diamond (Iowa) and square with diagonal lines (U.S.). The August 2011 forecast (fc) yield for Iowa is the same as the trendline yield, 177 bu/acre. The forecast (fc) yield for the U.S. is shown in the square with vertical lines. Data is from USDA-NASS.


Roger Elmore is a professor of agronomy with research and extension responsibilities in corn production. He can be contacted by email at or (515) 294-6655. Elwynn Taylor is extension climatologist and can be reached at or by calling (515) 294-1923.

Weather Impact on Midwest Corn 2011

Elwynn Taylor and Roger Elmore, Department of Agronomy

A break in the Midwest heat storm is a good thing, but is it good enough for the corn crop? A few days of temperatures exceeding 93 F – like we experienced in July – are “bad” for corn production, but  consecutive days of the high temperatures are especially bad. When the heat comes as silking gets  underway – as it did this year – the negative aspect is increased. Our mail indicates that ears did not pollinate well in at least major parts of fields across the Midwest and the locally grown sweet corn we have been consuming verifies that there are pollination problems this year. Many reported silking problems in late July. Shallow kernels, missing kernels, and tip back are common in field corn this year. All of this unfortunately sounds similar to what we experienced last year.

Pollination and kernel set problems in northeast Iowa. Photo by Brian Lang, ISU Extension.

Corn development and temperature

As of Sunday, Aug. 7, 73 percent of Iowa’s corn was good to excellent condition, a significant change  from 82 percent the week ending July 10 (USDA-NASS). The percent of Iowa’s corn silking and corn in or past the dough stage were slightly behind last year but slightly ahead of the 5-year normal. Some fields have reached the dent stage seemingly one to two weeks ahead of schedule. Remember though that kernels contain about 45 percent of their drymatter at dent and  normally another month is necessary to complete the crop’s development. Fortunately the weather outlook for the next 10 days indicates that temperatures are likely to be on the low side of normal in the Corn Belt east of Des Moines, Iowa (Figure 1). The precipitation outlook shows a tendency toward normal for Iowa and neighboring states but less than normal rainfall for the areas further East, South, and West. 

Figure 1. The outlook shows cooler than usual temperatures for Aug. 14-19 for northeast U.S. (also near the Pacific coast) and above normal temperatures are likely to the north and east of New Mexico. 

Most areas in Iowa will have a reprieve from the heat during the next 10 days. However, the reprieve will not restore the loss of potential crop yield that was incurred by faulty pollination or by the accelerated pace of grain maturity. Areas south of I-80 will likely return to above normal temperature (Figure 2) during the week of Aug 16-22. Precipitation will be normal to dry from west to east across the Corn Belt.

Figure 2. The 8 to 14 day outlook (August 18-22) indicates a likelihood of warmer than usual temperature across the Corn Belt to the south of I-80.

One year ago the higher than usual night-time temperatures after silking likely resulted in a yield reduction of about 10 percent (below that expected from the general condition of the crop). The high temperatures of 2011 have added more complexity to the development of the crop. Heat and water stress at pollination resulted in:

  1. Poorer pollination than was noted in 2010
  2. More hours of leaf-rolling of corn resulting is about a 1 percent yield loss for every four hours of rolling during the week of pollination and a 1 percent yield loss per 12 hours of rolling during other developmental stages of the crop
  3. The accelerated maturity following pollination appears to be more significant in 2011 to date than it was during 2010

Producers can estimate the accelerated maturity influence from computed growing degree days. On the Mesonet IEM Ag Weather/Climate Information site  simply select a weather station near your area of interest (they are shown on a state map or listed by nearby city) and begin the computation on July 1. Construct graphs for 2009, 2010 and 2011 if you wish to estimate the effect on your crop for comparison with the previous two years.

Figure 3 shows the normal growing degree day accumulation from July 1 to Aug. 8 for Ames, Iowa as a red line. The figure shows a blue line of accumulation for 2009 that is below the normal and resulted in yields that generally exceeded the expected. During 2010 the accumulation was greater than normal and the yield was reduced by about 10 percent (in excess of other stress effects that the crops may have experienced). The 2011 accumulation to date is about twice that of 2010 and the impact on yield may also be about double for the location shown. Remember, the accelerated accumulation of growing degree days shortens the time from silking to maturity and this generally reduces the yield because of a reduced number of days that the crop is gaining kernel dry weight between silking and maturity.

Figure 3. Accumulation of Growing Degree Days at Ames, Iowa from July 1 to Aug. 8.
During 2009 the accumulation (lowest curve) was below the normal “red” line and the grain filling period was somewhat longer than usual. During 2010 the accumulation exceeded normal and the shortened filling period resulted in a somewhat reduced yield. The 2011 accumulation (top curve) appears to be about twice the 2010 amount to date. The graphic is a composite of three graphs generated at the Iowa Mesonet website. Choose “single site graphs” and enter the year, starting date (July 1 for example), and the ending date (any date between July 1 and the day of computation).



Roger Elmore is a professor of agronomy with research and extension responsibilities in corn production. He can be contacted by email at or (515) 294-6655. Elwynn Taylor is extension climatologist and can be reached at or by calling (515) 294-1923.

Iowa Learning Farms and ISU Extension to Host Field Day Aug. 25

By John Lundvall, Iowa Learning Farm

Iowa Learning Farms (ILF), Iowa State University (ISU) Research and Demonstration Farms and ISU Extension are hosting a field day at the ISU Agricultural Engineering and Agronomy Farm, near Ames, Aug. 25, from 9 a.m. to 2:15 p.m. The field day will feature strip-tillage and precision agriculture technology.

Attendees will be able to learn about all aspects of strip-tillage, network with farmers who have been using this practice, talk with experts about crop issues and see in-field strip-tillage and precision agriculture demonstrations. Admission is free and lunch is included.

With the implementation of strip-tillage, landowners and farmers should see better water infiltration, improved soil structure, and potential for reduced fuel, machinery and other crop input costs. Before planting (fall post-harvest, or spring pre-plant) a strip-tillage implement creates strips of tilled soil. Surface residue is left undisturbed between the tilled strips. Corn or soybeans are planted into the tilled soil strips, which warm and dry faster than the rest of the field, making this system ideal for some Iowa soil types.

Farmers wanting to plant continuous corn should consider the strip-tillage features of soil conservation, controlled wheel traffic and fuel savings. Farmers are producing top-end continuous corn yields with a single fall or spring strip-tillage pass. Guidance systems allow the farmer to control specific strip placement from year-to-year, either splitting previous year’s planted rows or planting on top of the previous year’s rows.

Field day schedule

Field day guests will rotate between two morning and two afternoon sessions. The morning sessions include Matt Darr, ISU agricultural and biosystems engineering department assistant professor, who will discuss and demonstrate precision agriculture technology and equipment and Mark Hanna, ISU Extension agricultural engineer, who will discuss strip-tillage equipment and take questions from attendees. Guests can also visit with several implement company representatives and see in-field strip-tillage demonstrations.

After lunch, ISU Extension corn agronomist Roger Elmore and ISU Extension plant pathologist Alison Robertson will be on-hand to answer questions of crop concerns. Attendees are encouraged to bring samples of ears or plant leaves so that these experts can better identify problems and solutions. The field day offers plenty of time for attendees to network and learn from soil and crop experts.

Alternate route

Due to reconstruction of U.S. Highway 30, access to the ISU Agricultural Engineering and Agronomy Farm on Aug. 25 will be re-routed. Organizers of the event offer the following alternate directions because direct access to the farm from the Highway 30 is closed:
• Coming from the west, exit at Highway 17 east of Boone, travel south one mile to 240th Street (gravel), turn left and go two miles east to U Avenue, then north to the farm.
• Coming from the east, exit off Highway 30 at South Dakota Avenue near west Ames, travel south on South Dakota to 240th Street (gravel), go west five miles to U Avenue, then north to the farm.


John Lundvall is the Iowa Learning Farm field coordinator. He can be reached at 515-294-8912 or by emailing

This article was published originally on 8/15/2011 The information contained within the article may or may not be up to date depending on when you are accessing the information.

Links to this material are strongly encouraged. This article may be republished without further permission if it is published as written and includes credit to the author, Integrated Crop Management News and Iowa State University Extension. Prior permission from the author is required if this article is republished in any other manner.