IMMAG Updates

October 2016

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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Happy Haul-o-ween!

Upgrade to New Version of RUSLE2
A newer version of RUSLE2 software (version is available for FIELD USE.  The instructions (PC based computers, Windows 10 Operating System) for how to save your prior work, download and install the new version, and import in your prior work are available on IMMAG web site.  All service providers are required to use this version.  If you have not already upgraded to this newer version, please consider installing RUSLE2 Version  Updates in this version include minor bug fixes and updated user access (acc files), user templates, and print templates.  The irrigation subroutine, inadvertently turned off on the previous version, has been reactivated.  A new soil import procedure has been installed so that ALL users can import soils data directly from the official NRCS soil database.  In case you are currently not using it, please consider referring this information to your acquaintances working with RUSLE2.  RUSLE2 is used in conservation planning, and for calculating and completing Iowa Phosphorus Index (P-Index).  P-Index is then used in nutrient management plans, comprehensive nutrient management plans, and manure management plans.

Science Behind 50-degree Soil and Nitrogen Application
When applying ammonia rich manures, like swine manure, you should wait until soil temperatures at the 4-inch depth are 50°F and cooling to avoid potential loss of nitrogen. While all forms of nitrogen can be lost, ammonia and nitrate tend to be the most mobile forms. Since ammonia is lost as a gas, when applying an ammonia rich manure, it is especially important to get the fertilizer into the soil quickly through injection or immediate incorporation. The ammonia will react with the soil particles and be held, rather than sitting on the soil surface and potentially being lost to the air.
Nitrogen in the form of nitrate can then be lost with water, especially water moving through the soil to groundwater or tile drains. While manure tends to be nitrate free when it is applied, microbes in the soil will process it and turn it to nitrate. The activity level of the microbes is controlled by how much ammonia is present, the amount of water and oxygen in the soil, and the soil temperature. Soil temperature plays a critical role. Microbial activity will double for every 18°F increase in temperature. This means not only will the microbes have more time to convert ammonia in the manure into nitrate, the conversion may be faster than if the manure application had waited until the soil temperature reached 50°F.
A summary to illustrate this effect is shown in Figure 2 below. This figure illustrates nitrate-nitrogen losses in tile drainage water from three different swine manure application strategies. These were an early fall manure application (early October), a late fall manure application (at approximately 50°), and an early manure application that was then planted to cover crop. Results indicated timing of application reduced nitrogen losses in tile water slightly, but use of cover crops with manure reduced nitrate leaching substantially.
Learn more about the science behind waiting until soil temperatures at the 4-inch depth are 50°F and trending cooler here.
Iowa State University Extension and Outreach maintains a statewide real-time soil temperature data map on their website that can be used to determine when fall applications are appropriate. Current soil temperatures can be found at

Road Safety
As manure application season continues, don’t forget to take precautions when driving on public roads. During October through December, nearly half of all collisions involving farm vehicles take place. Majority of these accidents are either a rear end collision, when the approaching vehicle hits the farm vehicle from behind, or when a passing motorist attempts to pass a farm vehicle that is making a wide left turn. Additionally, accidents involving farm equipment are more likely to produce a fatality.
Below are a few tips to help keep you and others safe this application season:

  • Determine where additional reflectors, lights, and mirrors are needed for wide loads
  • Replace cracked lenses and burned out bulbs
  • Clean manure or other debris from reflectors, light lenses, and mirrors before entering public roads
  • Avoid busy routes and busy times of the day
  • Don’t text and haul

Use caution when agitating deep-pitted manure
Hydrogen sulfide gas continues to be a serious issue both in and around barns with liquid manure storages. The decomposition of organic matter in manure results in the release of several gases; ammonia, carbon dioxide, methane, and hydrogen sulfide among them. Most of the time these gases are emitted slowly, but any time manure is being agitated, pumped, or the surface is disturbed, hydrogen sulfide can be rapidly released. Although all are potentially dangerous, hydrogen sulfide tends to be the one of most concern in these cases. Hydrogen sulfide has an intense rotten egg smell, so it is relatively easy to detect its presence, even in very low concentrations. However, since we can smell it at such low levels, there is not a clear indication of when it reaches a potentially hazardous conditions that we can detect without the use of analytical instruments.

Hydrogen sulfide can spike quickly and without warning during pit pumping and agitation. Aggressive agitation can contribute to the risk of gas spikes when agitation first begins and when the pit becomes nearly empty. Your manure agitation technique can make a big difference in how much, and how quickly hydrogen sulfide is off-gassed from the manure. This fall there have been several incident resulting in cattle death in Eastern Iowa, Western Illinois, and Southwestern Wisconsin.
Below are a few best practices regarding manure agitation.
People should NEVER enter a building being pumped. Use yellow caution to mark barn entrances to block door or consider lockout tags during pumping. If possible, remove animals before pumping. For barns with multiple pits move cattle out of the room with the pit being agitated.

  • Don’t agitate until manure the manure level is 1 ½­ to 2 feet below the slats.
    • Hydrogen sulfide is denser than air and as a result will tend to pool on the manure surface, sufficient separation is required to minimize hydrogen sulfide in the animal breathing zone.
  • Avoid aggressive agitation when animals are in the building (no rooster tailing).
    • Surface agitation causes more turbulence and greatly increases the release of hydrogen sulfide.
  • Do not direct agitator nozzles toward pillars, walls, or towards a corner.
    • Pillars and walls stop flow quickly and cause the manure to churn, increasing the rate hydrogen sulfide is off gassed from the manure.
    • Corners are often dead air zones; releases of hydrogen sulfide in this area are more likely to result in animal loss
  • Stop agitating when bottom nozzle is less than 6” below the manure surface.
    • Keep the agitation below the surface at all times.
  • Avoid sudden changes in agitator depth and intensity.
    • Quick changes can result in large amounts of solids that haven’t previously been agitated and result in rapid gas release.
    • Slower changes in both power, flow direction, and depth, allow slower, more continuous release that is safer for animals and workers.

To help ensure that you and your employees are safe purchase hydrogen sulfide monitors to alert you to hazardous levels. A list of several available models is provided below.

Registration for Soil Health Conference Available
The two-day soil health conference from February 16-17, 2017, will be held in Ames at the Scheman Building. Efforts towards this conference are being coordinated by Mahdi Al-Kaisi, Iowa State University Extension and Outreach soil management specialist. The theme for the conference is “Building Soil Health for Healthy Environment and Farm Profitability.” Conference topics will cover a wide range of interests to farmers, agronomist, students, policy makers and the general public.  A number of well-known and established scientists from Land-grant Universities, the USDA, and industry have been lined up as conference speakers. During the two-day conference, information provided by speakers will be useful decision-making resources for best soil management practices that can be helpful in building healthy soils for sustainable agriculture, healthy landscapes, and communities with stronger agricultural economies. CCA credits will be offered to conference participants who are eligible. The conference will host poster presentations and a call for posters is available at the conference website.


The Livestock and Poultry Environmental Learning Center is hosting a webcast on Friday, November 18 at 1:30 PM about A Nutrient Management Training Course for Farmers: A Vermont Case Study. For more information on this webinar click here.

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

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

Rachel Klein
(515) 294-6685

Melissa McEnany
(515) 294-9075

Iowa Manure Management Action Group

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