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8/24/2009 - 8/30/2009

The 2009 Season in Degree Days Through Late August

By Rich Pope, Department of Plant Pathology and Elwynn Taylor, Department of Agronomy

Degree days are a critical driver of crop development, and 2009 certainly illustrates that point.

Wet soils and cool early season temperatures delayed some plantings and also delayed the development of crops that were planted on time. The early vegetative stages were slowed by cooler-than-normal temperatures, then July arrived with a remarkably un-summerlike chill that lasted the whole month. 

Crop stages remained stagnant for three weeks, with corn silking and soybean pod set both delayed by ten days to two weeks in most areas. Because the weather is one major variable that we cannot change, but only observe and take action based on those observations, comparing 2009 with previous years is at least interesting, if not instructive for harvest-season planning.

The graph below illustrates the march of departures from long-term average degree day accumulations for 2009 and selected other years. The graph depicts the three most recent seasons; includes 1992, 2003 and 2004 - three years that some have compared with 2009; and 1994 - a year that generated remarkably good yields.


degree day deviations


The graph shows the progress of the seasons in ten-day periods, starting on May 1. A line segment that rises indicates an above-average 10-day heat accumulation, while one that falls gained less-than-average heat. Several observers have suggested that seasonal heat accumulation trends in 1992, 2003 and 2004 through mid-August all experienced significantly colder weather than average, quite similar to the current season. Remember that getting a bit ahead in development before the reproductive stages initiate is generally an advantage (up to 200 or 250 GDD ahead of normal), while falling 100 to 250 GDD behind during the reproductive stages is also often an advantage in that it extends the time of grain filling, assuming that day-time temperatures exceed 75F.  Such was the case in both 1994 and 2004. In 1992 yields were very high but the total GDD accumulation was not sufficient for the crop to reach full maturity and very wet corn was harvested.

Degree days and previous crop performance as taken from archived outlying research farm reports for the representative years are summarized here:

1992 – May 1992 was a bit above normal, but that was the end of that.  Once June came, week by week found us falling more and more behind in degree day accumulations. We did receive ample rain in July and August, but the cold slowed crop development considerably.  Frost came to central Iowa late in September, and although both corn and soybean crop yields were quite good, slow or inhibited dry down and resultant grain quality issues were a considerable and costly.

1994 – The year was one of above normal temperatures during the vegetative period, followed by a cool July and August, with September (dry-down) again warmer than average. Rainfall was generally favorable throughout. The result was a year that set record (for the time) crop yields, and fairly good harvest conditions.

2003 – Some have compared 2009 (to date) with 2003. Rain in May and June 2003 was normal (2009 was generally above normal). Temperatures and rainfall were conducive to good pollination but August went downhill with unseasonably warm and dry weather stressing fields when 10 days topped 90 degrees. Yield cutting soybean aphid populations also damaged many acres. Fall harvest weather was pretty good. Corn yield and quality were good.  However the heat and aphids took a bite out of soybeans and yields were generally disappointing.

2004 – The spring was about average for heat accumulation, but a bit on the wet side. August was quite cool (no above-90 degree days) and September was dry and about average to a bit above in heat accumulation. Killing frost in central Iowa came on Nov. 3. This was a good crop year, but there was more than usual regional variation across the state.

2006 – Yields were good to excellent for corn and about average for soybeans. Planting was on schedule, and we had a dry June followed by a hot July when the mercury topped 90F for 15 days. Timely rainfall in August helped in most parts of the state.

2007 – The year started with a very wet spring. Precipitation was above normal for most of the year, and stored water helped set the stage for flooding in June, 2008. Heat and moisture stress from the consistently warm season was averted by the consistent rainfall. Both the yield and quality was mostly average for both corn and soybean.

2008 – Last year many Iowa farmers were kept in limbo by excessive rainfall and flooding early in the season. Wet conditions delayed and prevented planting on many acres, especially in central and eastern Iowa.  The crop progressed slowly, but from early July to early September we received timely rain and adequate - hot but not excessive - heat. Mid-September was warm and favorable for dry down, and yields were pleasantly good for most.

2009 (to date) – This year will be remembered in part for a wet spring and some planting delays, and the first or second coldest July on record, depending on the criteria for comparison. Vegetative crop stages lagged in most areas, and two or three weeks passed in early July with the corn or soybean growth stage not advancing much. Corn silking date was late, with corn not reaching R1 until the last week of July in many places. What we needed was some good rainfall and a second year of not to cold and not too hot weather.  And, so far, so good!  The USDA crop condition report issued Monday, August 24 listed Iowa corn AND soybeans as rivaling Nebraska as the best in the Corn Belt, with both at 79 percent rated good to excellent. 

So where do we go from here?  The jury is still out of course, but at least the judge has sent the jury instructions, and we have solid reason to hope. Remember that the delay in reaching silk and setting pods is an issue, and although we are filling kernels and pods now, we are racing the season to get to maturity. Barring an early frost, things should be OK, but dry-down may be an issue, as it was in 1992.  The difference is that August 2009 has been a bit more favorable for grain fill and maturation. 

We still anticipate harvest concerns with wet grain. Grain quality and storage issues will likely be concerns. We still have another month and time will tell.



Rich Pope is a program specialist with responsibilities with Integrated Pest Management. Pope can be contacted at or by calling (515) 294-5899. Elwynn Taylor is Extension Climatologist and can be reached at or by calling (515) 294-1923.



Webcasts Will Cover Water Quality Protection Issues

By Susan Brown, College of Agriculture

Water quality protection is the focus of two webcasts being made available by the Heartland Regional Water Coordination Initiative partners (Iowa State University, Kansas State University, University of Missouri, and University of Nebraska – Lincoln, the USDA and US EPA Region 7). Crop producers, resource managers and agency professionals can learn more about improving their practices to protect water quality by participating in the two 2-hour discussions, or later viewing the archived tapings of the sessions.

The first webcast, scheduled for 10 a.m. to noon Sept. 1, will explore the adoption and cost effectiveness of practices for water quality protection. Best Management Practices (BMP) for state specific issues will be covered by university researchers, including two Iowa State University presentations – Developing and Implementing a Cost Effective BMP Implementation Plan in an Iowa Watershed, presented by Chad Ingels; and Hypoxia – Improving the System in Iowa: Costs and Needs, presented by Jim Baker.

The webcast on Sep. 15, from 10 – 11:45 a.m., will discuss converting CRP grassland to crop production and pasture. The four speakers will present information on converting CRP to: corn and soybean rotation, wheat and corn in dry regions, pasture production, and with no-till methods.

The webcasts will be accessible at in combination with dialing (866) 433-4616. Once prompted for a “pass code followed by the pound sign,” enter 882477#. Participants will be able to submit questions and comments by typing into a ‘chat box’. 

Additional information on speakers and topics, and archived presentations are available on the Kansas State University website at .

A Top Ten List: Preparing for Fall Manure Application

By Angela Rieck-Hinz, Department of Agronomy

1. Review manure management plans. Prior to land application, review your manure, nutrient, or comprehensive nutrient management plan, make any necessary updates such as adding new fields. Review the plan, application methods and separation distances with employees and/or commercial manure applicators. Also consider evaluating fields for application. Because winter application of manure is prohibited for confinement feeding operations with liquid manure, plan ahead in the event you may have to apply manure under emergency situations in the winter. Save fields with the flattest slopes and P-Index ratings of 2 or less for emergency application.

2. Know and follow land application separation distances. Confinement site operators are subject to land application separation distances to neighbors and public use areas, but all animal feeding operations, regardless of size, are subject to separation distances from designated areas (water sources). Get a copy of an aerial photograph of your fields and the neighbors’ field to which you apply manure. Map out neighbors’ houses, churches, businesses, school, cemeteries and other public use areas as well as all designated areas such as sinkholes, wells, including abandoned wells, cisterns, designated wetland, water sources, high quality water resources, ag drainage wells, and tile inlets to ag drainage well. Identify all other sources of concern for manure application. Sketch out separation distances. Train your employees to read the maps and stay away from areas where manure is not allowed to be applied. If needed, flag out the areas in the field. Share copies of the maps with your commercial applicator. Make sure you understand the definitions for incorporated and injected manure. Make sure you understand separation distances for designated areas (water sources) must have the manure injected or incorporated on the same date it was applied. For more information see DNR 113 Separation Distances for Land Application of Manure and DNR 117 High Quality Water Resources.

3. Make sure manure applicator certification is current. If you are required by law to be certified to handle, haul, transport or land-apply manure make sure you certification status is current. Contact your local ISU Extension office to schedule an appointment to attend training. For more information see the ISU Manure Applicator Certification web page. If you are not sure of your current applicator certification status please contact the DNR Licensing Bureau at 515-281-5918.

4. Develop an emergency action plan. Manure spills happen, so plan accordingly. Train employees in manure spill response. Ask your commercial manure applicator if they have a plan of action in the event of a spill. If they don’t have a plan, demand it. Keep important phone numbers and contact information for excavators, neighbors with pumps and tractors, and local officials and emergency response units up-to-date and posted where everyone knows where to find them. Be aware of safety issues regarding gases when pumping and agitating manure. NEVER enter a building or manure storage when pumping or agitating manure. See the following resources for emergency action plans and safety related to manure gases.
• PM 1859 Emergency Action Plans
• IPPA’s Emergency Action Planning
• Iowa Farm*A*Syst Assessing Your Emergency Response Planning for Manure Spills
• Safety in Swine Production Systems

5. Take manure samples. Taking manure samples prior to land application will give you nutrient analysis results for planning application rates this fall. Sampling during land application or manure agitation may provide better results to use in future planning, but will not provide nutrient analysis results to use in planning application rates for this fall. It is important to build a history of nutrient analyses for manure sampling to help better manage the nutrients in manure for crop production. For more information, see PM 1558 How to Sample Manure for Nutrient Analysis.

6. Sample soil. Will you need to update an MMP in the next year or two where you need soil samples to re-do your P-index? If so, taking the required soil samples this fall will keep you from getting caught needing to update the MMP at a time you can’t get soil samples taken. Samples should be taken prior to manure application. For a MMP, one soil sample can’t represent more than 10 acres unless you are updating an existing P-index and have been applying manure at less than the P removal rate of the crop, then one soil sample can be taken for up to 20 acres.

7. Calibrate your application equipment. When the co-op applies fertilizer for crop production do they know how much they are spreading? Yes! Why not do the same for your manure nutrient source? Calibrating manure application equipment takes a little time, but in the long run it will help you meet the correct application rate and make better use of your manure nutrients. Available resources include PM 1948 Calibrating Liquid Tank Manure Applicators and PM 1941 Calibration and Uniformity of Solid Manure Spreaders.

8. Think timing, timing, timing. A new law has been passed prohibiting the application of liquid manure from confinement facilities on snow-covered or frozen ground during certain times of the year. However, regardless of the source of manure, or the size of operation, application of manure under these conditions is not recommended due to the increased risk of nutrient loss and movement to surface waters. IMMS Vol. 3 Winter Manure Application

9. Consider the neighbors. There is no doubt about it, the number one complaint about manure application is the odor. Right or wrong there is a perception of “if I can smell it, someone must be doing something wrong.” Work with your neighbors to let them know about your manure application plans. If possible, tell them how long it might take, how you plan to apply the manure, and how long they might expect to smell the manure. Inquire about any outdoor events in the neighborhood such as weddings, Friday night football games, cookouts and such to avoid manure application prior to those events. Good communication is the key.

10. Be safe. Fall is a busy time of year for farmers and commercial manure applicators. The last two falls in Iowa have been really short seasons of work due to long rainy periods, early snowfall and the ground freezing earlier than normal. Many manure spills happen because people are in a hurry or are tired from long hours of application work. Get plenty of rest, take breaks and slow down. Take time to inspect equipment. This will help protect employees and reduce the chances of equipment malfunction. Observe all laws of the road and watch out for the “other driver”. They may not realize you are moving at a much slower rate of speed or how long your tractor and tank wagon are when they go to pass you on the road. Check “slow moving vehicle signs” and replace as needed. Check lights to make sure they are working and are visible. Install additional lights as needed to improve your visibility and to help people see you.

This article originally appeared in the IMMAG Update email newsletter, August 2009.



Angela Rieck-Hinz is an extension program specialist for Iowa State University Extension and is the coordinator of the Iowa Manure Management Action Group (IMMAG). Rieck-Hinz can be reached at (515) 294-9590 or by emailing

Weekly Crop and Weather Report

By Doug Cooper, Extension Communications

Iowa State University Extension climatologist Elwynn Taylor, integrated pest management specialist Rich Pope, and soybean agronomist Palle Pedersen are the Aug. 24 weekly crop and weather report guests.

Taylor says the ocean's temperature is reported to be the warmest since 1909 and that could lead to an increase in tropical storms. These are storms that could impact Midwest weather patterns.

Pope repeats his recent message - late season crop diseases are being reported and scouting is still recommended.

Pedersen says soybean aphids are very spotting; they are beyond threshold in several Iowa counties and spraying is underway. Big question is when to stop spraying for aphids. This is a perfect year to check varieties for sudden death syndrome and determine varieties for future years.

Degree Days - Entering the Stretch, Aiming for the Finish Line

By Rich Pope, Department of Plant Pathology

Another week of cool but not too cold weather has positioned the Iowa grain crop well for the final run to harvest.  During the week of August 17 we lost a net 50 to 60 degree days to average, but favorable night temperatures allowed for crop condition to improve slightly. The August 24 USDA crop condition report assesses Iowa corn and soybean both at 79 percent good to excellent. Another two or three weeks of good weather and we will begin the final dry-down push to harvest.

Degree day accumulations through August 23, 2009

Most soybeans have now reached growth stage R5 to R6 and corn is at R3 to R5. We are near the peak of whole plant dry matter accumulation, and the last phase of grain fill is the mobilization of carbohydrates into the developing seed.  See the ICM article that compares the 2009 growing season with selected previous crop years.


Rich Pope is a program specialist with responsibilities with Integrated Pest Management. Pope can be contacted at or by calling (515) 294-5899.

This article was published originally on 8/31/2009 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.