Application Methods

Application: used for during field application of manure to reduce odors and emissions

Pros

• Potential to reduce odors and emissions
• Injection and incorporation can conserve nutrients.

Cons

• Soil disturbance can potentially increase erosion.
• Requires more horsepower for injection or incorporation.
• Costs may be greater for injection versus broadcast applications.

Description

Land application is an important contributor to the emissions from animal agriculture and has the potential to be a significant source of emissions of gases and odors. It is believed that up to one third of the total ammonia emission can occur during land application of manure.  Reducing emission can retain more nutrients for crops and thereby be economically prudent. Even when the production site is well-sited to minimize odor impacts on neighbors, land application may occur somewhat near neighbors and provide an opportunity for odors to become problematic.

Figure 1. Solid manure broadcasting.

There are several basic methods used to apply manure to cropland. Solid manure, like that from poultry, beef feedlots or other bedded systems, are generally broadcast onto fields (Figure 1). This may be incorporated using a tillage operation such as disking or harrowing. Liquid or slurry manure, like that from swine or dairy operations, has several application options including irrigation, broadcasting on the surface with or without incorporation and injection.

Broadcasting manure, either solid or liquid, without incorporation, results in the highest emission of gases and odors. An emission reduction between 20% and 90% can be realized by simply incorporating manure through tillage immediately, generally within 24 hours, after the manure has been applied. These reductions are thought to be as high as 60% to 80% for liquid manure if they are accomplished within 6 to 12 hours of the initial application.

Figure 2. Applying manure with a tanker equipped with and injection toolbar.

Injection of liquid manure reduces emissions of ammonia and odors by up to 90% over broadcasting alone. Hanna et al (2000) found that there was no significant difference in odor between fields where manure was injected and recently tilled un-manured fields.  Injection may be accomplished with either a tanker with an injection toolbar (Figure 2) or an umbilical or drag-hose system (Figure 3), where manure is pumped to the toolbar from a remote location.

Figure 3. Umbilical or drag-hose system applying manure.

Umbilical systems tend to be used by larger farms that have application land within a few miles of the swine or dairy production site or by commercial contract applicators. More equipment is required and heavier usage tends to make the cost more competitive. With either the umbilical or tanker equipment the method of injection equipment varies and includes the use of chisel shanks, sweeps, shallow disks or narrow knives (Figure 4). Results do not indicate a consistently best method and the choice should be influenced by which method may retain crop residue cover on the field. This tends to be a greater issue in soybean stubble. When injecting, caution should be used when turning on end rows. If manure is allowed to be uncovered on end rows (broadcast) it will cause odors. Even though it is on a relatively small portion of the field, it is often closest to roads and tends to be the most visible area. This may also result in over-fertilization of end row areas. Another possible downside of injection is that nitrous oxide emissions can be increased due to anaerobic conditions in the soil where manure is deposited.This may be an acceptable tradeoff in light of the significant reduction of ammonia emission. Manure application is not a significant source of methane emission.

When using irrigation to apply manure odor and emission control is difficult. Low trajectory guns or drop-nozzles that produce large droplets will help to reduce the odor and emissions. Center pivots should use low pressure nozzles. Avoid using big-gun irrigation systems because of large odor and emission potential from small droplets sprayed high in the air. In light of the emission and odor potential, irrigation of manure is best avoided.

Transportation to the field can be a source of odor as well. Cover solid manure during transport to reduce odors. Avoid any spillage on roadways or at the pumping site.

Figure 4. Injector with covering disks.

Effectiveness

In general, research work on manure additives have shown inconsistent results, potentially due to differences in methodologies used by the researchers as well as differences in manure properties used in the testing. When considering the different additives available, asking about what work they have performed, and the additives that were used (microbial, adsorbents, oxidizers, acidifiers, others), is a good method to evaluate the products effectiveness.

Cost Considerations

Injection is typically more costly than broadcasting due to increased horsepower requirements and equipment requirements.  According to Muhlbauer et al (2008) the cost for using a drag-hose or umbilical system was about 166% of a broadcast system.  However, some of that increase in cost may be recaptured through increased nutrient retention for crops or due to extra cost for tillage to incorporate manure that was broadcasted.

References

Hanna, H.M., D.S. Bundy, J.C. Lorimor, S.K. Mickelson, S.W. Melvin and D.C. Erbach.  2000.  Manure incorporation equipment effects on odor, residue cover, and crop yield.  Applied Engineering in Agriculture 16(6):621-627.

Lorimor, J. 1998. Iowa odor control demonstration project: Soil injection. Iowa State University Extension Publication PM 1754E, Ames, IA.

Muhlbauer, R., J. Puck, B. Puck and R. Burns.  2008.  A review of manure injection to control odor and ammonia emissions during the land application of manure slurries.  IN: Mitigating Air Emissions from Animal Feeding Operations Conference Proceedings. pp. 238-244. May 19-21, 2008.  Iowa State University, Ames, IA.

Powers, W. 2004. Practices to Reduce Hydrogen sulfide from livestock operations. Iowa State University Extension Publication PM 1972a. Ames, IA.

Livestock and Poultry Environmental Learning Community:

Air Emissions After Manure Land Application Including Subsurface Application of Poultry Litter and Solid Manure
Manure Application Method and Timing Effects on Emission of Ammonia and Nitrous Oxide