Nutrient Management and Water Quality in Poultry Operations

William Owens  |  1/8/2018 4:54:44 PM

William E. Owens

The poultry industry in Louisiana is the No. 1 animal commodity. Poultry generates approximately $2 billion for the Louisiana economy and is second only to forestry for all commodities. With this increase, new challenges have arisen. Handling and disposal of poultry waste are major issues for the poultry industry. Poultry waste includes poultry manure, litter, bird mortality and waste from hatcheries and processing plants. Poultry best management practices have been developed to guide producers in the most efficient, safe and economical methods for handling poultry waste.

The LSU AgCenter Hill Farm Research Station in Homer, Louisiana, includes two demonstration houses that can compare and evaluate the latest innovations in equipment and management techniques for raising poultry broilers under commercial conditions. Recently, the demonstration houses were used as the focal point for projects outlined in a National Resources Conservation Service grant designed to evaluate poultry management practices. Key aspects of the grant included evaluating the impact of fan dust on water quality, comparing in-house pasteurization of poultry litter to conventional stacking and educating producers.

Fan dust is the accumulation of dust and fine debris generated by air flow through the houses. The dust tends to accumulate just outside the exhaust fans. The dust is composed primarily of fine poultry litter and is considered a possible point source of pollution by the U.S. Environmental Protection Agency. Test results indicated that fan dust caused a localized increase in nitrates in runoff water but did not exceed established limits of 10 milligrams per liter. There was also a localized slight increase in phosphorus but no increase in total nitrogen. In this demonstration, grass buffer strips were shown to be an important management tool to mitigate water quality problems (Figure 1).

Poultry litter is the poultry bedding and poultry waste that accumulate in the house as each flock grows. After each flock, some of the litter is removed, and new bedding is added prior to the next flock. Periodically, all of the litter in a house is removed and new bedding is added. The removed litter is usually stacked outside the house in a covered litter barn until it can be applied to the land as fertilizer. Many broiler producers reuse litter from previous flocks to help reduce the amount of litter for disposal and to help defray production costs. In-house pasteurization of broiler litter can be a good management tool to allow reuse. In this process, the litter is pulled into long windrows within the house. Each row is approximately 1.5 feet high and 4 feet wide. The poultry litter will then self-heat or compost, resulting in a reduction of moisture, ammonia and bacterial pathogens. This process, when properly done, allows the litter to be reused safely.

While poultry litter is a waste product, it is also a valuable source of nutrients and a much sought-after fertilizer (Figure 2). Poultry litter is heavily used as a replacement for commercial fertilizer on pastures and row crops. Proper use of poultry litter as a fertilizer requires sound management techniques to properly apply the litter and prevent water quality problems.

Important facts and guidelines for proper use of poultry litter as a fertilizer include:

  • Poultry litter needs to be analyzed for nutrient content before being applied to an agricultural field because not all litter is the same. A good expectation is a fertilizer equivalent of 3-2-2 (N-P2O5-K20). However, the actual nutrient content depends on the type of bird, what the birds are fed, the number of flocks grown before the litter is removed, the feed efficiency, and how the litter is stored and handled.
  • Not all nutrients in litter are immediately available to plants. Most of the nitrogen is in an organic form and must be converted by microorganisms before plants can use it. About 9 to 10 percent is inorganic and immediately available. This helps make the litter a slow-release type of fertilizer, distributing the available nitrogen over the growing season.
  • Poultry litter is rich in phosphorus, which is good if the soil is low in phosphorus but can present environmental problems if the soil is already high in phosphorus. High phosphorus levels in the soil have been directly linked to water quality problems.
  • Soil analysis needs to be done before poultry litter is applied to the field. This will help avoid overapplication of nutrients and allow the most economical use of the litter. If soil testing indicates high phosphorus, then the local extension agent should be contacted for help to determine the proper management plan for the soil to avoid water quality problems with phosphorus. One option may be to alternate use of poultry litter and commercial fertilizer as a nitrogen source. Another option is to use litter to meet the phosphorus need of the field and to then use commercial fertilizer to meet the additional nitrogen need. These practices can help reduce the water-quality effect of excess phosphorus in the soil.
  • Poultry producers need to develop a nutrient management plan. Both the EPA and the U.S. Department of Agriculture encourage a voluntary approach to handling nonpoint-source pollution related to animal agriculture. The implementation of a comprehensive nutrient management plan will ensure that the nutrient value of the poultry litter is managed in an environmentally friendly manner. Guidelines for developing a plan can be found in the LSU AgCenter publication “Poultry Production Best Management Practices” or by contacting an AgCenter extension agent.

Dead bird disposal is becoming an issue for the poultry industry. The recent avian influenza outbreak in the United States with the subsequent loss of large numbers of poultry focused attention on issues related to dead bird disposal. Previously used methods to handle dead birds include rendering, landfills, incineration, composting and burial. Rendering and landfills are restricted to locations near enough to existing facilities to be practical. Incineration requires special equipment and is costly, leaving composting and burial as the most practical alternatives. Burial has traditionally served as the most convenient method for disposing of large numbers of birds. It has the advantage of being relatively low-cost and usually can be accomplished at or near the site of loss. Burial pit dimensions and depths vary with state regulations and are also dictated by soil types and the number of birds to be buried. Groundwater contamination is a concern when burying poultry. Studies are needed to determine the effects of buried poultry on groundwater and to determine if new methods can mitigate those effects.

New studies are underway at the Hill Farm to evaluate new and different methods of bird disposal, including in-vessel composting (Figure 3) and shallow trench burial. These studies will compare methods of bird disposal and determine the most environmentally friendly and economical methods to handle bird mortality.

William E. Owens is the resident coordinator at the Hill Farm Research Station, Homer, Louisiana.

(This article appears in the fall 2017 issue of Louisiana Agriculture.)

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Figure 1. To demonstrate the impact of grass buffer strips, vegetation was suppressed in front of one collector (left) and left intact in front of the other (right). During a rain event, water flowed downhill toward the collection unit and was filtered by the grass buffer in front of the right collection unit. Photo by William E. Owens

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Figure 2. Poultry litter is periodically removed from houses and is then available for application on fields or crops as fertilizer. This photo shows the accumulated litter from the two broiler houses at the Hill Farm Research Station, Homer, Louisiana. This litter will be applied to hay fields and pastures as a fertilizer. Photo by William E. Owens

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Figure 3. In-vessel composters consist of a large vessel designed to hold mortality loss from poultry houses. The dead birds are added to the vessel along with a carbon source such as wood shavings. The vessel turns slowly once daily to mix the contents, and the inside of the vessel is designed so that the contents move slowly to the outlet port. Air is periodically infused into the chamber, and the contents undergo aerobic composting. Temperatures typically reach 140 degrees F, which is sufficient to destroy all bacterial and viral pathogens and reduce the contents to a useable mulch. The expelled mulch is rich in nutrients and has no objectionable odors. It can be spread on pastures is a similar manner to poultry litter. Photo by William E. Owens

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Test burial pit fitted for water and soil analysis at the Hill Farm Research Station in Homer, Louisiana. Photo by William E. Owens

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