IMMAG Updates

May 2017

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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Manure Application Uniformity

photoMaybe you have seen some tweets and pictures about manure application uniformity testing over the past years, or hopefully seen some information about upcoming field days where uniformity is going to be a key topic. You might be wondering why we are making a big deal about this, but when it comes to using manure as a fertilizer effectively, understanding how uncertainty impacts your decisions is critical for making the best management decision. To hear more about uniformity and how it can impact your crop performance take a look at The Manure Scoop.

Late Spring Nitrate Test

To reach the goals set by the Iowa Nutrient Reduction Strategy, consider utilizing split fertilizer application. Split fertilizer application can increase nutrient efficiency and reduce nutrient loss. Additionally, there is less investment in the field if forced to replant to soybeans after weather-related losses or planting delays. This may allow time to gather additional information about the year’s market and growing conditions. The cost of making a second fertilizer application trip across the field and potential for rainy weather are deterrents of spring nitrogen application.

Often, when switching to split application, the general plan is 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 the sidedress amount using the late spring nitrate test (LSNT). The late spring nitrate test is a nitrate only soil test. It should be done when the plant is 6-12 inches in height; this allows for spring nitrogen losses or gains to be reflected. Soil samples are taken at a depth of 12 inches. The test provides information on plant-available nitrogen concentrations in the soil before the plant begins rapid uptake of nitrogen.

table of nitrogen fertilizer recommendationsResearch recommends 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. One of the challenging parts of using the late spring nitrate test is determining the "critical" soil nitrate concentration you are trying to achieve.

In manured fields, a "critical" soil nitrate-nitrogen concentration of 15-20 ppm is recommended. This is lower than non-manured fields because manure application provides additional organic matter that will be mineralized after the time of soil sampling and becomes available to plants later in the season. Using the results, calculate the amount of nitrogen that would be recommended to sidedress. The formula for calculating nitrogen application is if the 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 SP 0435A - Reducing Nutrient Loss: Science Shows What Works.

Alternative Poultry Housing Styles - Impact on Manure Properties

photo 2The U.S. egg industry has been evaluating alternative hen housing systems, such as enriched colony and aviary houses; to meet specific animal welfare regulations often related to space and activity needs of the animal. However, the impact these changes have on environmental footprints of these operations (for example, air emissions) and the manure generated in the facility is often unclear. However, a recently published study by Shepherd et al. (2015) provides results from the study of three commercially operated egg production systems over a couple of years. The study monitored a conventional cage housing system, an enriched colony housing system, and an aviary housing system. All located on the same farm and with the same type of hens. The study found the house level of emissions of ammonia were highest in the aviary system at 0.112 g/hen-day, followed by the conventional cage (0.082 g/hen-day), and then the enriched colony housing system (0.054 g/hen-day). These houses all used manure belts equipped with manure-drying air ducts above the manure belts. In the study, running manure belts every two days would significantly reduce ammonia loss from the manure providing a relatively easy management strategy to hold onto nitrogen and make the manure more valuable.

In addition to evaluating barn-level ammonia emission, they also studied ammonia loss from the manure storage. Finding the aviary manure emitted an additional 0.188 g/hen-day and the conventional cage manure an additional 0.208 g/hen-day while the enriched colony manure only emitted 0.106 g/hen-day more ammonia. In all, the 60-70% of the farm’s ammonia emission was from the manure storage area and reducing emissions from this storage could be important for keeping the manure at its most valuable. One trend was noted, if the manure was drier when it entered the manure storage, ammonia emission was lower.

Beef Manure - How does your production system impact manure quality?

photoIn raising beef finishing cattle, there are a lot of choices in housing style, ranging from open lots to confinement buildings with slatted floors and bedded packs. Each has pros and cons in how the cattle are handled, the cost to construct, and cattle performance, but it also impacts the manure properties. On average, only about 10-20% of the nitrogen and phosphorus feed a steer is retained for growth. The rest is excreted in the manure. However, the housing system picked and the manure management methods can have a big effect on what happens to the nitrogen and phosphorus. For example, the typical finishing steer space results in about 122 pounds of nitrogen excretion per year, depending on the housing style only 66 to 98 pounds will be available to land apply. Check out more at The Manure Scoop.

Compost, Stockpiling, and Fresh Manure – What is happening?

photoHandling systems affect manure nutrient levels and forms by influencing gaseous emissions, exposure to runoff and leaching, and as a result can influence a manures ability to supply crop nutrients when land applied. Traditionally on feedlots in Iowa pens are cleaned periodically and then the manure is stockpiled, either near the lot or in a field and then eventually land applied. In some cases, lots might be scraped frequently and the manure land applied almost immediately. So what difference does each of these make to the manure properties? Learn more at The Manure Scoop.


June 2, 2017 - Manure Distribution and Calibration Field Day, Puck Custom Enterprises, Manning
Puck Custom Enterprises field day will have morning activities starting at 9:30 am about injector tillage options, technology sessions on the control system being used to control application rate and improve safety to protect water quality.

June 23, 2017 - Manure Distribution and Calibration Field Day, ISU Allee Research and Demonstration Farm, Newell

June 29, 2017 - Iowa Swine Day, Scheman Building, Ames

July 26, 2017 - Manure Distribution and Calibration Field Day, Zoske’s Sales and Service, Inc., Iowa Falls

August 4, 2017 -- Manure Distribution and Calibration Field Day, Eldon C. Stutsman, Inc., Hills


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

Rachel Kennedy
(515) 294-6685

Melissa McEnany
(515) 294-9075


Iowa Manure Management Action Group
Twitter: @iowamanure

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