Author: M. Benjamin Samuelson, Agronomy graduate student, University of Nebraska-Lincoln

In 2019 a Costco chicken plant and its associated growers will begin operations in the region surrounding Fremont Nebraska. We are fortunate to have access to a deep knowledge gained from other poultry producing regions. Eastern Nebraska has the opportunity to make beneficial use of broiler house manure, a new addition among fertility resources for our region.

Because of the organically-bound nutrients and associated carbon in broiler manure, it has the potential to improve nutrient use efficiency and soil function, like water infiltration, when compared to commercial fertilizer. In specific cases, broiler barn operators may benefit from further composting their manure. This article describes broiler manure and its direct land application, as well as scenarios where further composting may be useful. Either choice has its own benefits and best practices.

What is broiler manure, and how much manure is produced in the region?

Growers maintain production units, each consisting of four barns, and each generating 1,200 tons of broiler manure annually. After the development of 2019, A total of 108 units will generate about 130,000 tons of broiler manure annually – enough to supply nitrogen fertility for about 32,000 acres of productive corn fields¹.

The most prominent difference that sets broiler manure apart from other manures is its relatively high concentration of nutrients per ton, making it more affordable to haul and apply per unit fertility delivered. What makes it so different?

First, chickens consume a more nutrient-rich diet, so they excrete a more nutrient dense dropping. Furthermore, birds are more efficient in their use of water. Their kidneys recover more water from waste, leaving behind the white part of a bird dropping which packs a dense punch of nitrogen compared to the urine of mammals. Finally, broiler manure is dry, crumbly, and partially pasteurized by the way it is handled inside the barns.

The handling of manure inside the barns has a strong impact on its properties. Broiler barns are bedded with wood shavings. After each flock is harvested the bedding, droppings, spilled food, and feathers are stacked into windrows inside the barn. These rows naturally heat up to 140-150 F, and are turned 2-3 times according to temperature. This destroys most chicken pathogens, and dries the mixture allowing it to serve as bedding for the next flock.

Broiler litter contains approximately 40% moisture when stacked. After 16 days, the material is spread back across the barn floor, new wood shavings may be added and the next flock enters the barn onto a bedding with approximately 25% moisture. Six flocks pass through each barn annually. Periodically between flocks, a portion of the bedding is removed after it is windrowed, for example one out of four windrows may be removed before the remaining three are spread as bedding. Typically, once a year all litter is removed and new bed of clean wood shavings are added to the barn.

Due to the feed requirements, physiology, and bedding management regarding broiler chickens, their manure is low in moisture and high in plant nutrients. In fact it offers about five times the nitrogen and three times the phosphorus per ton compared to beef feedlot manure. If the comparison to feedlot manure is a useful one, two safe generalizations follow: First, more of the fertility value in poultry manure is in an inorganic form, immediately available for plants, and making application timing more important for optimizing nutrient use efficiency. Second, slightly less soil-building carbon comes along with the NPK in poultry litter than feedlot manure, but broiler manure still contributes organic matter unlike commercial fertilizer.

What is broiler compost, and why is compost so distinct from manure if they are essentially made of the same thing?

Compost is a fairly general term which refers to the result of an aerobic digestion of organic materials. In composting, microorganisms chemically transform fresh organic materials from their original state. A portion of the resulting compost material either is, or was, a microorganism. The same is true of stable soil organic matter.

It is worth noting that by some definitions broiler manure, in its form after removal from barns, is compost. It may be more accurately described as partially composted manure. “Compost” is not a very specific term, and there several critical factors that make any particular compost suitable or unsuitable for any particular application. Compost attributes beyond NPK fertility are especially important for floriculture, greenhouse, nursery, and indoor applications.

Broiler manure exits the barns as a partially composted product. It has been heated by microbial activity while in turned windrows, which destroys most animal and plant pathogens and stabilizes a portion of the soluble nutrients present in fresh manure. Decomposition is slowed as windrows dry which makes the material more suitable for re-use in the barns as bedding. As harvested, broiler manure contains 10-15% of its nitrogen in ammonium form.

If a producer were to continue the composting process to completion, additional water and oxygen would need to be provided to decompose the manure further, until microbial activity drops to a low and relatively constant rate.

Fully composted animal manures are distinctly different from their fresh counterparts. More organically-bound phosphorus is present in compost, and nitrogen in compost is almost exclusively in an organically-bound form, with ammonium levels well under 1% of total nitrogen. The result is that nutrients are less mobile, less prone to leach or runoff, and less quickly available. Plants only access nutrients supplied by compost when they are digested or ‘mineralized’ by the microbes in soil which happens constantly and gradually, accelerating with warming soil temperature. So the fertility is more available when plant growth is more rapid.

What would make further composting of broiler manure a good idea?

Three targets for good compost mixture must be achieved to reduce odors, greenhouse gasses, and nitrogen loss while keeping process time low. The first is a moisture content of 40% to 60%, second is aeration (sufficient ‘bulking’ to maintain air-filled pores under the pile’s own weight, and lastly carbon to nitrogen ratio should be between 25-40:1. If poultry litter is to be composted, it is valuable to have a laboratory test the poultry litter for nitrogen and volatile solids (divide volatile solids by 1.8 to estimate carbon content) to determine carbon to nitrogen ratio. As producers will use their own discretion when adding wood shavings as bedding between flocks, carbon:nitrogen will vary. If enough bedding is used, it is possible that some operators will have manure in target range for carbon:nitrogen and bulking that can be composted with only water input.

In the case of most animal manure, there is a dramatic surplus of nitrogen and shortage of bulking material, and in the case of broiler manure there is also a shortage of moisture. If the material removed from our new broiler barns is to be composted, simply stacking windrows, adding moisture and turning them could result in tremendous losses of nitrogen. Up to 77% of nitrogen can be lost (as an ammonia loss into the air) in composting (Martins and Dewes).

To finish composting of dry, fine-textured broiler manure (after partial composting in the barn), quantities of carbon-rich bulking material may need to be imported and water added. This may be costly, likely unprofitable unless the imported material is a waste for which the producer could charge a disposal fee (like municipal yard waste) and/or the finished compost finds a willing market for its added value (like landscape or nursery enterprises).

So will any producers choose to further compost manure once it is removed from the barns? “No, probably not” says Willow Holoubek, grower engagement manager for Lincoln Premium Poultry. Commercial egg-layer producers sometimes choose to compost manure. In a layer system, there is no bedding, and no windrowing step. The result is a heavier, wetter manure which is more difficult to handle and spread mechanically. In this case composting can help.

If compost is produced from broiler operations, the resulting product will have higher moisture, less fertility per ton, and as a result greater cost to haul per unit of fertility value. On the other hand, it will be odorless, less prone to nutrient loss by runoff or leaching, and cause less problems if over-applied (both to the crop and the environment).

In short, a composted broiler manure product would be valuable for residential, landscaping, or specialty crop use, but cost of production and transport make it difficult to justify for field crops such as corn.

The big picture

Whether composted or fresh, animal feeding operations deliver manure to surrounding agricultural land within practical hauling distance. For many manure-producing regions this has resulted in phosphorus over-loading. Phosphorus over-loading is the greatest concern for surface water quality for any land manure application. Historic poultry regions have created elevated phosphorus runoff risk over the decades. Meanwhile as a historic grain exporting region, many eastern Nebraska soils now struggle to maintain sufficient levels for phosphorus. In the case of the concentrated fertility of broiler manure, a great area of land can utilize these manure nutrients. And in the case of eastern Nebraska, a great deal of cropland that has scarcely received manure in decades will have manure available. The result will be less reliance on imported phosphorus fertilizer and risks associated with phosphorus runoff will be very manageable for our region. As with any nutrient management plan, regular monitoring of soil fertility and careful application will protect yields and the environment.

¹ Assumptions: 1,200 tons manure/4 barn set/year; 63 lb N per ton, 70% long term availability (Payne and Zhang), 180 lb N/acre.

Further Reading:

“Composting Manure and Other Organic Materials.” University of Nebraska – Lincoln Extension, IANR NebGuide G1315.

“Maximizing Poultry Manure Use Through Nutrient Management Planning,” University of Georgia Extension, Bulletin 1245.

References:

Andy Schulting, personal communication, October 29, 2018

Harris, Tyler. “Eastern Nebraska gears up for poultry production.” Nebraskafarmer.com. Aug. 3 2018.

Martins, O., Dewes, T., 1992. Loss of Nitrogenous Compounds during Composting of Animal Wastes. Bioresource Technology 42, 103-111.

Payne, Josh and Hailin Zhang. “Poultry Litter Nutrient Management, a Guide for Producers and Applicators.” Oklahoma Cooperative Extension Service Division of Agricultural Sciences and Natural Resources - Oklahoma State University, E-1027. http://poultrywaste.okstate.edu/Publications/files/E-1027%20REV%20061512.pdf

Ritz, Casey W, and William C Merka. “Maximizing Poultry Manure Use Through Nutrient Management Planning,” University of Georgia Extension, Bulletin 1245. http://extension.uga.edu/publications/detail.html?number=B1245&title=Maximizing%20Poultry%20Manure%20Use%20through%20Nutrient%20Management%20Planning

Shapiro, C. A., R. B. Ferguson, G. W. Hergert, C. S. Wortmann, D. T. Walters. “Fertilizer Suggestions for Corn.” University of Nebraska – Lincoln Extension EC 117. http://extensionpublications.un

Tomlinson, P., D. Shoup, D. R. Diaz, K-State Agronomy eUpdate – Nutrient Availability in Poultry Manure. Issue 666 December 31^st, 2017. https://webapp.agron.ksu.edu/agr_social/m_eu_article.throck?article_id=1635

Vadas, P. A., J. J. Meisinger, L. J. Sikora, J. P. McMurtry, and A. E. Sefton. “Effect of Poultry Diet on Phosphorus in Runoff from Soils Amended with Poultry Manure and Compost.” Journal of Environment Quality 33, no. 5 (2004): 1845. https://doi.org/10.2134/jeq2004.1845.

Willow Holoubek, personal communication, October 29, 2018. Wholoubek@lincolnpremiumpoultry.com

Wortmann, Charles S., Charles A. Shapiro. “Composting Manure and Other Organic Materials.” University of Nebraska – Lincoln Extension, IANR NebGuide G1315. http://extensionpublications.unl.edu/assets/pdf/g1315.pdf