Poultry Manure Handling - A Practical Approach

Rich Smith, Agricultural Engineer, Regional Advisory Services/Poultry Team - Alberta Agriculture, Food and Rural Development

[ Introduction | Waste or Resource? | Poultry Manure Characteristics | Poultry Manure Handling Systems | Use of Poultry Manure | Manure Handling Alternatives | Conclusion ]

Introduction

Despite the financial pressures facing many of our livestock and poultry producers, there still seems to be a great deal of optimism about the potential for growth in these sectors of the agriculture industry. This growth would follow a period in which there already has been a significant increase in the size and intensity of many livestock and poultry enterprises. Future development very likely would continue this trend toward large operations.

Unfortunately, one aspect of these livestock and poultry operations that has not kept pace with the increased intensity is manure management. We still are handling manure in much the same way as producers did when they cleaned their small barns and spread the manure on nearby fields. The volume of manure certainly has increased and the equipment is bigger, but the management process has not been refined very much. Producers and agricultural specialists recognize the value of manure, both as a fertilizer and a soil conditioner, but it has no real market value. As a result, many producers simply are trying to dispose of their manure as cheaply and on as small a land area as possible.

Given current economic conditions, least cost disposal may represent a practical approach to poultry manure handling. However, producers must ask whether this approach is sustainable. In this time of growing environmental awareness, producers must balance the effects of economic forces with increasing demands coming from outside the industry. There is strong pressure on all industries to reduce the production and disposal of wastes. Since simple disposal of organic by-products such as manure will become increasingly difficult and expensive, we need to find a better practical approach.

Waste or Resource?

While the question of whether manure is a waste or a resource does not rank with "to be or not to be" as one of life's burning issues, it is a very important consideration in manure management. People who deal with environmental issues like to use the phrase, "a waste is simply a resource in the wrong place." When that resource gets into really the wrong place, it becomes pollution. Every year, we see examples of manure being a resource, a waste, and a pollutant. Since our society tends to dispose of wastes and manage resources, the way that people view and handle manure will be affected tremendously by the answer to this question.

Waste disposal is a cost to all businesses, including livestock and poultry operations. The goal of waste disposal, then, is to minimize the cost to the business. This is how much of our manure currently is being handled. The methods used by businesses to reach this goal will be governed only by the societal and environmental standards that are imposed on the industry.

On the other hand, proper resource management brings profit to a business. Thus, the goal of resource management is to maximize returns from the use of resources. Resource management strategies will be based on economic decisions made withing the business. This is the direction in which our manure handling must head in order for our livestock and poultry operations to be sustainable.

What are the limitations to using manure as a resource? Sadly, the product has real value to soil and plants, but little or no cash value to farmers. Manure is a bulky product that has a relatively high moisture content and comparatively low concentrations of nitrogen, phosphorus, and potassium. It contains undesirable contaminants, has a high odour nuisance potential, and is not easy to apply at an optimum rate or location. Nevertheless, these limitations will lose importance as improved handling techniques and rising fertilizer costs make manure a more attractive alternative.

So the answer to this question is that manure is not totally a waste or a resource right now. Our present handling practices range from operations where producers place great value on their manure and manage it accordingly to farms where the producers dump their manure on land as thickly as possible. Generally, though, manure is seen as a product that is too valuable to be considered a real waste, but not valuable enough to be a true resource.

Poultry Manure Characteristics

The first step in good management of any product, whether for resource use or waste disposal, is understanding the nature of the material. The material itself often will dictate the allowable methods and rates of use or disposal. A practical approach to poultry manure handling must be based on knowledge of the manure.

One of the problems all producers face in handling manure is the highly variable physical and nutrient characteristics of the product. In the poultry industry, further variation is introduced by differences in species, housing systems, and bird age. Even within a specific operation, the characteristics of the manure will influenced greatly by the ration, the use of bedding, the manure handling system. The table on the following page, derived from the Code of Practice of Practice for the Safe and Economic Handling of Animal Manures, contains average values for key manure characteristics. Producers must recognize, however, that these figures are averages of values that cover a very wide range.

In this table, the volumes are typical values of manure production for 100 birds. The yearly volumes have been developed from the daily figures using normal cycles lengths and frequencies. The total N includes both mineral (nitrate and ammonium nitrogen) and organic nitrogen, although the organic portion is not available to plants without microbial mineralization. Crop N is an estimate of the available nitrogen (usually ammonium) plus the portion of the organic nitrogen that is mineralized over the growing season. Since estimated losses of nitrogen through volatilization to the air have been subtracted from this value, Crop N is the best prediction of the nitrogen available from manure in the first year after application.

Poultry Manure Handling Systems

The four main components of a manure handling systems are collection, storage, treatment and use/disposal. These components are described below.

1. Collection
   In floor housing systems, the manure mixes with the bedding to form litter. There is no separation of the manure from the birds, but producers rely on the absorptive capacity of the bedding to maintain a good environment for the birds. In cage housing systems, manure falls into pits or on to conveyors. In pit systems, the manure remains in the barn until cleaning, while the conveyor systems allow more frequent removal of manure from the bird housing area.

2. Storage
   All handling systems involve some storage of the manure between the time it is excreted by the bird and final application or disposal. A storage system allows producers to hold manure until a convenient and optimum time for use of the product. Many livestock and poultry producers use long-term manure storages to avoid winter spreading and make maximum use of the available nutrients.
   In floor housing systems, the litter is removed at the end of each cycle and may be stockpiled until it is used. A similar system is used in deep pit houses, while manure from conveyor systems is stored in lagoons or concrete tanks. When manure is stored or stockpiled, consideration must be given to the potential for nuisance and environmental problems.

3. Treatment
   The Alabama Cooperative Extension Service defines treatment as any system used to reduce the pollution potential of the waste or to otherwise alter its original condition. Other than the normal biological decomposition processes (usually anaerobic) that occur during storage, very little treatment of poultry manure occurs in Alberta. Treatment of manure costs money and often does not produce a very valuable product. As long as we have the capacity to make good and safe use of our manure, there likely won't be strong interest in treatment systems. A more detailed discussion of treatment will follow in the manure handling alternatives section.

4. Use/Disposal
   At this time, the most practical use of manure is to spread it on agricultural land where the organic matter and nutrients can be beneficial to the soil and plants. When manure is applied at a rate greater than that which the soil and crops can use, we view this as manure disposal. In disposal situations, producers really are using their fields as landfill sites. Those nutrients that aren't used by the crops can be released into the atmosphere and local water supplies where they can cause significant environmental impacts. While disposal seems like an inexpensive handling system, it very likely is not sustainable.

Use of Poultry Manure

If the most practical use of manure is to apply it to agricultural land, the best way to manage this resource, then, is to ensure that the timing, rate and method of manure application provide optimum growing conditions for plants. This means that manure should be applied as close to the growing season as possible, given weather and storage constraints. On annual crop land, manure usually is applied in the fall, after harvest, or in the spring, before seeding. Spring application probably is best for protection against runoff and loss of nutrients, but many farms do not have sufficient time available before seeding. Manure application on forage or pasture land can take place over the whole growing season, but should occur during periods when runoff potential is low and plant growth is strong.

The application equipment should be designed to distribute the material as evenly as possible at a location in the soil where plants can use the nutrients. Solid manure is spread on the soil surface, while liquid manure can be spread, sprayed, or injected. Incorporation of the manure into the soil is a recommended practice. This will reduce the losses of nitrogen to the air and eliminate the potential for nutrients to be carried away by runoff water. Since incorporation is not possible during winter months, on forage crops, or in no-till cropping regimes, extra care must be taken when manure is applied to these fields. In all cases, the potential odour nuisance of the manure should be considered in decisions regarding the timing and method of application.

For best resource management, the rate of manure application should be based on the principle of nutrient management. Nutrient management involves balancing the nutrients added to the soil by fertilizers and manure with the nutrients removed from the soil by crops. The nutrients supplied by crop residues, mineralization and existing soil fertility are included in this balance, as are the nutrients lost through leaching, volatilization and soil microbial activity. Using the nutrient management concept, producers can apply manure and fertilizers at rates that will contribute to optimum plant growth.

Excess addition of nutrients, a situation that commonly happens during manure disposal, can lead to significant environmental impacts. Nitrogen is the nutrient that has attracted the most attention among people monitoring the environment. Excess nitrogen can be lost to the air as ammonia, a pollutant, while the nitrate form is very mobile and can be leached into groundwater. For this reason, nitrogen usually is the limiting nutrient in determining manure applications rates.

Phosphorus is less mobile than nitrate nitrogen and tends to bind with soil particles after it is incorporated. However, phosphorus is a serious problem in surface water supplies and can be carried into these sources by erosion or runoff from unincorporated manure. In some areas, phosphorus has replaced nitrogen as the nutrient causing the greatest concern. Potassium levels can be high in soils where heavy manure application has occurred, but this nutrient generally does not cause environmental problems.

Notwithstanding the possible environmental damage, excess application of nutrients is wasteful. The extra nutrients do not enhance crop production and can, in some cases, even inhibit growth. Proper nutrient management clearly makes sense, at least agriculturally, but acceptance of this principle has been slowed by economic and educational factors. As long as producers are viewing manure handling as a waste disposal problem, nutrient management will not be a relevant concept. Even when producers accept this principle, a lack of knowledge and equipment limitations make full implementation difficult.

The following table provides a series of recommended rates and land bases for poultry manure application. The rates and acreages have been calculated using average values of Crop N and three levels of nitrogen application typically used in the dark brown/brown, black, and irrigated soil zones. Obviously, a knowledge of soil fertility, manure nutrient content, and crop requirements is a critical part of determining correct application rates. Producers also must recognize that nitrogen from manure continues to be mineralized for several years after application. Although the use of average values provides a reasonable starting point, they should conduct regular tests on both soils and manure to ensure that a nutrient balance is being achieved.

Manure Handling Alternatives

There are a number of reasons why producers are examining alternatives to the standard practice of spreading manure on agricultural land. Many poultry producers live on land bases that are not large enough for them to apply manure on the basis of nutrient management or even waste disposal. These producers must rely on the use of neighbours' land for manure application and rarely are compensated for the cost of this process. In some areas, the total production of livestock and poultry manure is greater than the area of land available for the use of this material. Other producers are interested in adding value to the manure or reducing the costs and environmental impacts of normal manure handling practices.

1. Marketing Manure
   Although growing acceptance as a valuable soil amendment and increasing costs of other fertilizers should increase the commercial value of manure, producers certainly can speed this process through more aggressive marketing of their product. This involves both selling manure as a resource and finding customers who wish to purchase. Arrangements with neighbours where manure is applied to land from which feed is purchased would be one example. Using custom operators or better equipment to ensure that manure is applied properly would help sales. Groups of producers could work together on collecting and distributing manure. Marketing takes more time and effort than producers typically have devoted to manure handling, but it may become necessary and the possible benefits are substantial.

2. Composting
   Composting of organic by-products and wastes is rapidly gaining favour all over North America. Indeed, the composting of poultry mortality is the subject of another presentation at this workshop. In the case of poultry litter, composting produces a more uniform and odourless material that can be used as a soil conditioner and slow release nutrient source in a wide variety of applications. Composting reduces the weight, volume and moisture content of manure, a huge advantage for any producer paying to have manure hauled to neighbouring land. The process also tends to prevent the germination of weed seeds, a problem often associated with the use of manure.
   Given these advantages, why aren't all poultry producers composting their manure? Composting costs money, even in simple windrow systems, and the product produced by this process often is not valuable enough to justify the extra expense unless standard manure handling practices have become too costly. There are good markets for compost in the horticulture and reclamation sectors, but the business is competitive and margins are small. Identifying and entering these markets can require tremendous effort. One application that has significant potential for producers living near urban or industrial areas is the mixing of poultry manure with municipal or industrial organic wastes to produce compost. The manure would be a nitrogen source that could be added to high carbon wastes to create favourable C:N ratios. In these co-operative ventures, the other partners would share the costs of composting and assist with marketing the product. These partners often find disposal of organic wastes to be very expensive and would be happy to contribute financial support to alternatives.

3. Treatment
   A number of other manure treatment and processing alternatives are available, but these are rarely economical or practical. Treatment of manure with chemicals and aeration tends to reduce the odour, but can be very expensive and generally adds no value. The production of biogas from the anaerobic decomposition of poultry manure is physically possible, but it is a complicated and expensive process that is far from economical at our current energy prices. There has been extensive use of poultry litter for cattle feed in the past, but food safety concerns could preclude the use of this alternative. Unless the costs and returns of these treatments and processes change radically, they are unlikely to become practical alternatives in the near future.

Conclusion

In considering the topic of poultry manure handling, there was uncertainty over whether the focus should be on improvements to existing practices or on exciting new alternatives. A practical approach, however, dictated that the emphasis be placed on enhancement of standard practices. If poultry manure handling can be moved further along the path from a waste disposal to a resource management process, along with the prudent use of composting, producers will be in a good position to ensure the environmental sustainability of their industry.