IMMAG Updates

May 2015

Welcome to the monthly update for the Iowa Manure Management Action Group (IMMAG) Web site. This update is provided as a service to inform you about changes made to the IMMAG Web Page or items of interest dealing with manure management and air quality from animal feeding operations. If you wish to subscribe to this mailing please click here. You may also view this update with direct links on the CURRENT NEWS site on IMMAG.

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Livestock Odor – What options are out there?

photoSpring is here, crops are planted, and another graduation season has arrived, and with it the beginning of another outdoor party season. However, the return to outdoor living can bring odor issues back to the forefront. When it comes to odors, some are generated by the poultry and livestock, some may be generated by the feed, but the majority of the potentially objectionable odors tend to come from manure, either its storage or when it is land applied. There is no single technology or quick fix available to solve our odor issues, but there are many different techniques that have been tried and researched.

Recently a team of Iowa State University Extension and Outreach specialists developed an online tool that can help compare in comparing different odor mitigation techniques. This tool is called the Air management Practices Assessment Tool, or AMPAT, and is available at The goal of the tool isn’t to push any one method of odor control, but rather to help understand what some of the options are, where they may be appropriate, and how effective they might be.

"The website was developed to help livestock and poultry producers identify practices to reduce odors, and emissions of gases and dust on their farms caused by animal production," said Angie Rieck-Hinz, an ISU Extension and Outreach field agronomist and member of the project team. "The database lists options to be used from three core sources of odor and emissions in their operations - animal housing, manure storage and handling, and land application." Other members of the team include Jay Harmon, Steven Hoff and Dan Andersen, professors of agricultural and biosystems engineering at Iowa State.

To use the tool, go to the website and choose an odor-source category (animal housing, manure storage & handling, or land application). You will be taken to a page that lists some different odor mitigation techniques that are appropriate to that odor-source category, as well as relative rank of their effectiveness in mitigating different gases. Remember, just because it shows up on your list as potentially appropriate for that odor-source, doesn’t mean it will work for you. For example, compositing is listed under the manure storage and handling category, but this technique is only appropriate for solid manures, so it may not integrate easily if you have a liquid manure system. Clicking on a specific mitigation practice that interests you lets you learn more about its effectiveness, relative cost, and provides a variety of resources, including a research-based publication on the practice, the pros and cons of using it, and a short video about how it works.

"If a producer was concerned about a potential odor problem from animal housing, he would scan down the list under the ‘odor’ column at the top," Harmon said. "From the list, he would find that ‘Siting,’ ‘Scrubbers,’ ‘Urine/Feces Segregation’ and ‘Biofilters’ have green bars, meaning they have high impact on odors. With that information, the producer could then investigate options for implementing those technologies, evaluate their selection based on relative cost, or investigate all four options for their farm as they learn more about what might work best for them.

Development of the tool was completed by an Iowa State University Extension and Outreach project team with major funding from the National Pork Board.

Nutrient Management Spotlight - Late Spring Nitrate Test

This year as part of the Manure Applicator Certification program, we asked you what you were doing as part of the Nutrient Reduction Strategy to reduce nutrient loses from your farm. One of the more popular answers was switching to split fertilizer application. Some potential benefits of split fertilizer application may include reduced opportunity for nitrate loss through leaching and denitrification, the potential to use less fertilizer, having less investment in the field if you are forced to replant to soybean after weather related losses or planting delays, or even slightly delaying to get additional information about this year’s markets and growing conditions. However, there can be concerns about the costs of making a second fertilizer application trip across the field, or even if the weather will permit this fertilizer application.

Often times when we switch to split application our general plan is be to apply 50-60% of the nitrogen recommendation in the fall or early spring, and then to sidedress the remaining 40-50% into the growing crop. An alternative approach is to determine our sidedress amount using the late spring nitrate test (LSNT). The late spring nitrate test is a nitrate only soil test where soil samples are taken to a depth of 12 inches when the corn plant is 6-12 inches tall. This test is supposed to inform us about available nitrogen concentrations in the soil just as our corn growth, and nitrogen need, is about to take off. In using the results you’ll want to break your field up into different management zone, parts of the field that have similar management histories and soil types (a management zone probably shouldn’t be any bigger than 10 acres). Within each management zone 16 to 24 soil cores should be collected. As these samples are collected you need to make sure that any banded fertilizer or manure isn’t biasing your results; sampling in a pattern relative to the corn (or banded fertilizer) row can help eliminate the effect of the banded application. For example, go to the first sampling location in your management zone and pull the first soil sample in the row, then move to your next sampling spot and pull the soil sample one-eighth the distance between rows, go to your next sampling location and pull the sample one-fourth the distance between rows, and continue this pattern.

Although this may seem a little complicated, the real difficulty starts in interpreting the results. Iowa State research says corn needs 25 ppm of nitrate-nitrogen in the top 12 inches of soil to produce maximum yield; however, the interpretation of the results vary with cropping system, manure history, and even weather conditions prior to and after sampling. Selecting the “critical” soil nitrate concentration (the one you are trying to achieve) is one of the more difficult parts of using the late-spring nitrate test to make management decisions.

Table 1. Nitrogen fertilizer recommendations for corn on manures soils.

Recommended N rate

Soil Test

Excess rainfall

Normal rainfall

ppm NO3-N

lb N/acre

lb N/acre










> 20



In fields that have received manure, a “critical” soil nitrate-nitrogen concentration of 15-20 ppm nitrate-nitrogen is recommended. You’ll note that this is lower than non-manured fields; this is because the manure application provided more organic nitrogen that will be mineralized throughout the growing season and become plant available, but isn’t detected by this test. Based on your sample results you can then calculate the amount of nitrogen that would be recommended to sidedress. The formula for calculating nitrogen application is if your soil test was greater than 20 ppm then 0, otherwise (20 ppm - soil test nitrate) * 8 = lbs of N/acre to apply. Alternatively, table 1 provides a way to select a sidedress nitrogen application rate. In this table excess rainfall would be May precipitation that exceeded 5 inches, normal rainfall should be used for other cases.

As with any new fertility management program, first-time users are encouraged to experiment with the test in small areas before using it to guide fertilization on all their fields. As with most recommendations this test is intended to maximize profits when used across many years and sites, not to give the “perfect” rate in a specific year.

For more information related to using the Late Spring Nitrate Test please see, ISU PM1714- Nitrogen Fertilizer Recommendations for Corn in Iowa. More information on best management practices for reducing nutrient loss from agriculture can be found in SP435 - Reducing Nutrient Loss: Science Shows What Works.


The March 1 deadline for renewing your manure application certificate has come and gone, so if you are a commercial manure applicator and were licensed in 2014, you will have to pay the late fee of $12.50 in addition to the regular certification fees.  If you are a confinement site applicator who is renewing your license in 2015, you will also have to pay the late fee in addition to the regular certification fees.  All new applicators (not previously certified) or confinement site applicators completing continuing education for their 3-year license do not have to pay the late fees.  If you missed training opportunities in January or February your two options to meet certification requirements include 1) contacting your County Extension Office to make an appointment to watch the appropriate training video; or 2) contacting your local DNR field office to schedule an appointment to take the certification exam. All certification requirements must be met prior to applying manure.


Avian influenza has been confirmed in Iowa and poultry producers are reminded that when a quarantine exists, permitting requirements for the movement of poultry and poultry products, including manure, are in effect. More information is available here on these policies. Additional resources on avian influenza and biosecurity tips are available on the Egg Industry Center website.


The IMMAG Events page is a compilation of manure management related events. Please check the events page often for new listings.

The USDA Natural Resources Conservation Service (NRCS) is hosting a webinar on May 19th at 1:00 PM on Using RUSLE2 to Accurately determine soil loss for conservation compliance. More information and a link to the webinar can be found here.

The Livestock and Poultry Environmental Learning Center is hosting a webcast on May 22nd at 1:30 PM where they will highlight research posters that were presented at the Waste to Worth conference recently.  To view the webinar live go here. As a reminder, past webcasts are available here.

Iowa Swine Day is being held on June 25 in the Scheman Building in Ames, IA. This is a gathering of leading experts who focus on topics vital to today’s pork industry. The morning will have sessions on the world protein outlook, communicating with the public, and audit issues, while in the afternoon there are options about learning more about PDEV and emerging diseases, a session on Hot topics (euthanasia, new feed regulations), and hearing about what is new in research at Iowa State University. More information and a registration link are available here.

North American Manure Expo will be held in Chambersburg, PA on July 14-15, 2015. The theme this is "Manure Than You Can Handle." The two day event will consist of tours on the 14th and vendor displays, educational opportunities, and manure technology demonstrations on the 15th. For more information or to register for the event go to; additional details are also available on their Facebook page.


Angie Rieck-Hinz
(515) 231-2830
Twitter: @iowamanure

Dan Andersen
(515) 294-4210
Twitter: @DrManure

Iowa Manure Management Action Group

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