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VI. Poultry Waste Management Programs

VI. Poultry Waste Management Programs

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by N and P in runoff, (3) long-term fates of heavy metals and pesticides on soils,

waters, and the food chain, and (4) pollution of drinking waters by pathogens

such as E . coli and subsequent effects on human and animal health. Clearly, the

environmental impact of greatest concern will be directly related to the use of

the poultry waste. Avoiding degradation of groundwaters and surface waters by

nutrients, pesticides, and pathogens is the most pressing issue associated with

land application of poultry wastes. Toxicological effects of these waste constituents are of more concern when the wastes are processed and used as animal


Sound waste management plans must reflect and prioritize the risks associated

with each end use to maximize resource value and minimize environmental impacts. The focus of the management practices discussed here will be the use of

poultry wastes as fertilizer materials for crop production. The literature on the

advantages and disadvantages of refeeding poultry wastes to ruminants is voluminous and exceeds the scope of this article, as does the use of wastes as fuels.

Readers are referred to several reviews of these topics (Fontenot and Ross, 1981 ;

McCaskey and Anthony, 1979; Shuler, 1980; Smith and Wheeler, 1979).







The components of an effective waste management program for the agricultural use of organic wastes are illustrated in Figs. 14 and 15 and include (1) site

selection, (2) production and collection, (3) storage, handling, and treatment,

(4) transfer and application, and ( 5 ) utilization. Legal and regulatory requirements must also be considered in designing a plan. Although there is no single

waste management plan that is appropriate for all locations, site-specific optimization of each of these components is essential to avoid wasting resources and

pollution of nearby environments. The localized nature of the poultry industry

in many areas also requires that regional waste management plans be developed

using the same principles as farm-wide plans. Whatever the scale, comprehensive waste management plans assist in identifying potential problems in waste

utilization and provide the basis for long-term plans for the most efficient use of

these potentially valuable resources. Some key aspects of each component will

be considered to illustrate the process involved in developing a waste management plan.

1. Site Analysis and Selection

Natural land features should be carefully considered when developing an agricultural waste management plan. As illustrated in Fig. 14, site analysis must




Existing contours




Figure 14 Typical site analysis for an agricultural waste management system. Adapted from

Soil Conservation Service (1992).

include appropriate locations for production, storage, and treatment facilities, as

well as the suitability of soils on the site for land application of wastes. Proximity

to streams, ponds, and drainageways and an understanding of groundwater hydrology are also vital components of site analyses, as are other potential environ-



Figure 15 Waste management options for a poultry operation. Adapted from Soil Conservation

Service (1992).

mental impacts such as odors, dusts, and noise. Flexibility is another important

design consideration. A well-designed plan allows for future expansion of the operation or incorporation of conservation measures such as vegetated filter strips

near streams.



2. Production, Handling, Storage, and Treatment

A waste management plan should have as one of its highest priorities the

minimization of waste generated. Any design feature that can reduce the volume

of solid waste or wastewater will facilitate the ease and efficiency of operation

of the plan. Examples include diverting clean runoff away from wastewater lagoons and avoiding spills of feed and other solid materials. Waste collection

should reflect the patterns of waste production and be closely tied to storage

capacity so that wastes can be stored in locations that are protected from rainfall

and runoff and are maintained in a physical condition suitable for the appropriate

application technique. Outside storage of broiler litters, for example, can result

in a wet material that is difficult to handle and apply uniformly and can contaminate the storage site with salts and NO,-N, making it unsuitable for crops and a

pollution threat for nearby waters. Treatment facilities, such as lagoons or composting facilities, should be properly constructed and have adequate capacity to

handle normal and unexpectedly high volumes of waste; they should also monitor waste properties to determine the effectiveness of the treatment operation.

3. Transfer and Application

Transportation of wastes to the site of ultimate use and application at the site

must be considered carefully. The unfavorable economics of waste transportation

often result in limited distribution of nutrients throughout a farm, causing the

buildup of some nutrients (e.g., P) to excessive levels in fields short distances

from the site of waste generation. Outdated or poorly maintained application

equipment can restrict the rates of waste that can be applied or result in poor

distribution during application. As an example, newer “spinner” type manure

spreaders can uniformly apply much lower rates of broiler litter than older, flail

type spreaders, allowing for more precise application of desired rates of N and

P. Timing of application to maximize crop recovery is another critical factor, one

that is closely related to production patterns and storage capacities. Application

of poultry wastes during fall and winter, when crops have not been planted or

are not actively growing, is normally discouraged. Unfortunately, during these

months, farmers have more time available for transfer and application operations

than during the spring when other operations (cultivation, planting, herbicide

application, etc.) are necessary. In some areas it is often necessary to apply

animal wastes when the soil is frozen to avoid compaction and erosion problems

that can result from heavy equipment traveling over the normally wetter soils of

spring. Poorly timed applications of wastes that result in excessive losses of

nutrients in runoff or by leaching are one of the most difficult challenges to

resolve. Computer modeling approaches to determine the most effective means

to schedule poultry waste applications to soils are being developed to help resolve this problem (Edwards et al., 1992).



4. Utilization

Maximizing the resource value of poultry wastes often requires a combination

of end uses. A common example of this is a small farm that produces more waste

material than is needed to meet the nutrient requirements of the crops grown on

the farm. In this situation, the poultry producer must identify other options to

avoid potentially contaminating surface waters or groundwaters by overapplying

nutrients to cropland. If options such as refeeding or incineration for energy

generation are not available, distribution to nearby farms or industries that market and apply wastes may be necessary. Well-established infrastructures to redistribute poultry wastes to nutrient-deficient areas are uncommon, however, particularly on a regional scale. In Delaware and Arkansas, for example, the

Cooperative Extension system, in cooperation with the poultry industry, has developed a local network for farmers that wish to obtain excess broiler litter from

nearby poultry operations. However, at this time, a comprehensive plan to deal

with the large excess of nutrients present in these states (Table IV) has not been


In most poultry operations, the first step in an effective waste management

plan will be an assessment of the capacity of available cropland for nutrients in

the wastes. Most nutrient management programs for animal wastes are similar to

those developed for sewage sludges and are usually oriented toward identifying

the appropriate application rate for a specific crop and field. However, unlike

municipalities that often apply sludges to a number of different farms, most

poultry growers have a fixed amount of cropland available to receive wastes. A

comprehensive, farm-wide nutrient budget is essential to ensure that waste production does not exceed the capacity of the entire farm for nutrients. Once an

efficient nutrient management plan has been designed, further steps can be taken

to identify alternative end uses for excess wastes.




Poultry wastes contain all essential plant nutrients, several nonessential heavy

metals, natural and synthetic organic compounds, and a variety of pathogenic

organisms; each of these waste constituents could conceivably limit the rate of

poultry waste application to agricultural lands. Current approaches to land application of litters, manures, and wastewaters, however, are almost exclusively

based on meeting crop nitrogen requirements, for several reasons. First, groundwater contamination with nitrate N in areas of intensely concentrated animal

production is recognized as a serious and documented environmental problem.

Second, although excessive P levels in soils that frequently receive poultry

wastes are common and the role of soil P in eutrophication of sensitive surface



waters is well-known, basing the application rate of poultry wastes on crop P

requirement creates serious logistical problems. The extremely low rates of manures and litters required, if any, to meet crop P needs result in large surpluses

of these wastes, often without adequate alternative end uses. In some areas,

however, as discussed in Section IV, concern about excessive soil P has resulted

in its use as a land-limiting constituent for poultry wastes. Third, limiting annual

or total application rates of poultry wastes based on the loading rate of nutrients

other than N or P is usually unnecessary because they rarely affect crop production or the environment. And finally, the lack of clearly documented, significant,

environmental impacts of heavy metals, pesticides, and pathogens has, at least

to this point in time, made their use as land-limiting constituents for poultry

waste application unjustified.

Nutrient management programs normally consist of four steps: (1) identification of crop nutrient requirements at realistic yields, (2) the use of soil testing to

estimate nutrients available for the crop from previous applications of fertilizers

and wastes, (3) an assessment of the nutrients that will be provided when the

waste is applied, and (4)efficient application techniques that provide the desired

amount of waste at the proper time to maximize crop nutrient uptake. Examples

of N- and P-based nutrient management plans will be given to illustrate these

steps and the fundamental differences in these two approaches to nutrient management. Recent advances in soil and plant testing that can improve the efficiency of nutrient management of poultry wastes will also be discussed.

1. Nitrogen Management Plans for Poultry Wastes

Current approaches to N management for poultry wastes normally base land

application rates on the amount of predicted or potentially available N (PAN)

needed to provide adequate N for a crop at a realistic yield goal. Waste management practices, based on local soil and climatic conditions, are then relied on to

minimize the excess amount of N required, as a result of anticipated N losses

(system inefficiency), to attain optimum yields. For most organic wastes the

application rate needed to provide &heproper amount of available N is estimated

by one of two approaches, the decay series or the fertilizer equivalence. The

decay series approach has been widely adopted as a means to estimate both initial

and residual availability of N in poultry wastes. A decay series is essentially a

quantitative estimate of the amount of N that will be mineralized from an organic

waste over a period of several years, and is usually based on laboratory N mineralization studies. Pratt er al. (1973) proposed a decay series of 0.90-0.100.05, for poultry manure, indicating that 90% of &heorganic N would mineralize

in the first year, 10% of the remaining organic N in the second year, and 5% in

the third year. Although use of a decay series is conceptually sound, it is obvious

that many factors can affect the success of this approach, including heterogeneity



of wastes, annual variations in climate, and cropping system effects (e.g., tillage

and irrigation), to name but a few. Further, as the decay series only estimates the

amount of N that will become available, some technique to adjust (increase) the

waste application rate to account for potential N losses by volatilization, denitrification, or leaching would be required. Multiyear field calibration studies are

essential to verify a decay series. Sims (1987) evaluated a decay series of

0.60-0.20-0.10 for broiler litter, in combination with an adjustment for volatilization losses of NH,-N, in a 3-year field experiment with irrigated corn. Results

showed that, although successful in producing comparable grain yields as fertilizer N, the efficiency of N recovery obtained was low enough to be of concern

from an environmental viewpoint, averaging 36% for broiler litter and 56% for

fertilizer N.

The fertilizer equivalence approach determines N availability in organic

wastes more empirically. Field studies comparing several rates of fertilizer N

and organic wastes are used to determine the amount of total N in an organic

waste needed to obtain yields or N uptake by a crop equivalent to that obtained

with fertilizer N. Results are expressed as an equivalent rate (kg N/ha) or as

a percentage of total N. A recent example of this approach was a 3-year field

study with silage corn that reported, based on silage yield, that the fertilizer

equivalence for dairy manure ranged from 73 to 122 kg N/ha or 27 to 47% of

manure total N; based on N uptake the fertilizer equivalence was 26-60% (Jokela, 1992).

Perhaps the most notable advances in recent years with regard to increasing N

use efficiency from organic wastes have been in the area of soil and plant testing.

An accurate soil test for N has been a long but elusive goal for soil scientists.

The complex and dynamic nature of N cycling has made it difficult to use chemical extractants to estimate N availability in advance of planting. Similar problems have prevented the adoption of rapid chemical tests for available N in organic wastes (Castellanos and Pratt, 1981b; Chescheir et al., 1986). Residual

tests for NO,-N have had a history of success in arid-zone soils, but not in humid

regions (Hergert, 1987). In 1984 a significant breakthrough in soil N testing

occurred that has shown the potential for markedly improving the efficiency of

organic N sources for certain agronomic crops. The presidedress soil nitrate test

(PSNT) was conceived and evaluated to address the problem of overfertilization

of N in the northeastern United States, particularly in fields with histories of

manure and legume use (Magdoff el al., 1984). The PSNT has four basic tenets,

summarized as follows: ( 1 ) all fertilizer N for corn, except a small amount

banded at planting, should be sidedressed when the crop is beginning its period

of maximum N uptake; (2) soil and climatic conditions prior to sampling integrate the factors influencing the availability of N from the soil, from crop residues, and from previous applications of organic wastes; (3) a rapid sample turn-



around (
normally not sample to a depth >30 cm. The PSNT has since been evaluated in

over 300 field studies in the northeastern (Magdoff et al., 1990) and midwestern

United States (Blackmer et al., 1989) and has been repeatedly shown to be successful in identifying N-sufficient soils. Some of the logistical difficulties associated with the need for a rapid sample analysis have been overcome by the development of “quicktest” kits and electrodes that can be used in the field (Jemison

and Fox, 1988). Even more encouraging are the results of a recent study with the

leaf chlorophyll meter, which showed that this extremely rapid, in-field measurement of leaf “greenness” was as accurate as the PSNT in identifying N-sufficient

sites (Piekielek and Fox, 1992). Another new approach to assessing N sufficiency for corn is the stalk nitrate test (Binford et al., 1990). This post-mortem

test uses the concentration of NO, in the lower portion of the stalk at corn maturity to identify fields that receive excessive N from fertilizers or manures.

The implications of these tests for organic waste use are straightforward, but

not simple. For most farmers poultry manure or litter would be applied according

to a decay series or fertilizer equivalence approach. A PSNT soil sample would

be taken and, if necessary, additional fertilizer would be applied via sidedressing. However, studies from soils commonly amended with animal wastes have

shown that often little or no sidedress N is required, even when manure was not

applied in the current year (Fox et al., 1989; Meisinger et al., 1992). Roth and

Fox (1990) found that the “economic optimum N (EON) rates” (N rate where

economic return on fertilizer N investment is maximized) for 11 fields with and

without long-term histories of manure use averaged 34 kg N/ha for manured

fields and 128 kg N/ha for nonmanured sites. Alternatively, for maximum environmental efficiency, farmers could apply a suboptimum rate of waste that would

be very unlikely to produce excessive soil N. A PSNT soil sample or leaf chlorophyll meter reading would be taken and the remainder of the crop’s N needs,

if any, supplied via sidedressing fertilizer N at a time when crop N uptake efficiency is high. The greatest difficulty with the PSNT approach to organic waste

use, apart from logistical problems associated with the rapid analytical turnaround, has been the presence of high percentages of soils that have been shown

to need less, or no, manure/sludge than is generated by the farm or municipality.

Simply put, these tests have shown that, particularly for animal-based agriculture, more N is often produced than is needed by the farming operation, given

the land available and the economics of waste handling and application. This

once again illustrates the need for organic waste management at a larger scale,

state or regional in scope, oriented toward redistribution of waste N to nutrient

deficient areas.

Nitrogen use efficiency can be improved by other means as well, although

efforts to control N losses under field conditions can be difficult and expensive



and may increase one form of loss while reducing another. The use of conservation tillage practices can be expected to reduce erosion and runoff losses of N.

Reducing water movement off a field, however, may increase infiltration and

perhaps N03-N leaching and denitrification. Surface applications of wastes may

also reduce soil-waste contact and accelerate waste drying, enhancing NH, volatilization but decreasing the rate of N mineralization. Other conservation practices that have the potential to reduce N losses include the use of winter cover

crops to trap residual N from wastes, and controlled drainage systems or artificial

wetlands to enhance denitrification in field border areas.

It has been possible to increase N recovery from fertilizers by the use of improved application techniques, timing, and placement (banding, sidedressing,

fertigation) or by developing more efficient or enhanced fertilized materials

(slow-release N sources, chemical nitrification inhibitors). Logistical and economic constraints, however, have hindered the widespread development of improved handling and application techniques for animal wastes, although some

progress has been made in waste processing, primarily in the areas of composting and pelletizing. As mentioned earlier, composting stabilizes the N in wastes,

decreasing the likelihood of N losses via leaching or denitrification, whereas

pelletizing provides a drier material with much greater flexibility in terms of

nutrient content and application techniques. Composting converts raw waste to

a more humuslike material, suitable for application at extremely high rates, but

with limited N supplying capability. Pelletizing can convert organic wastes into

enriched, fertilizer-like materials that have broader uses and fewer restrictions

on transportation and handling. The use of nitrification inhibitors with raw

wastes, or probably more effectively with pelletized materials, can increase the

efficiency of N recovery as well. Sallade and Sims (1992) found that adding

thiosulfate to a poultry manure-amended soil inhibited nitrification and thus decreased the likelihood of NO,-N losses by leaching or denitrification.

Composting and pelletizing represent the type of large-scale improvement

needed in the centralized processing and distribution of poultry wastes to create

additional end-uses that increase the geographic distribution of poultry waste


2. Phosphorous Management for Poultry Wastes

Best management practices for poultry wastes that focus on controlling N

losses will almost always result in continuous increases in soil P, as discussed in

Section IV. In general, approaches to reduce nonpoint source pollution of P from

agricultural soils have two major components. First, the transport processes by

which P moves from an agricultural field to surficial waters must be controlled

by conservation practices that minimize erosion and runoff. Minimum tillage



operations, grassed waterways, and field border areas are commonly used to

reduce particulate P losses, but are not always effective in controlling the loss of

the more soluble, bioavailable forms of P, such as dissolved P and P in fine

sediments (clays, fine silts). Second, in addition to controlling transport, processes to reduce the enrichment of soil particles and runoff waters by P must be

developed. Practically speaking this involves the use of nutrient management

programs that prevent soil test P levels from increasing beyond existing excessive

values, while attempting to develop crop rotation strategies that can enhance the

rate of depletion of P in these soils.

The overall strategy for the environmental management of P for agricultural

operations that routinely use animal manures should be a systems approach with

the components discussed in the following sections.

a. Develop a Farm-Wide Nutrient Budget

The initial step in effective environmental management of P is the acknowledgement that a field, farm, or even region in a state may not possess adequate

soil resources to use all the P generated by animals and municipalities, as clearly

illustrated for Delaware in Table IV. It is therefore imperative to, on each scale,

develop a quantitative P “budget” that clearly delineates the amount of P available for land application, the current P status of the soil, and crop removal under

realistic yield conditions. The amount of P available can be estimated from manure production and P content, although some doubt exists as to the current

accuracy of farmer estimates of quantity and timing of manure production. A

detailed soil testing program should then be conducted that will quantify existing

soil P levels and the rates of manure or fertilizer P required to adjust all soils on

the farm to an optimum P level. Sims (1986a), based on crop removal studies

under greenhouse conditions, estimated that from 4 to 15 years would be required for soil test levels of P to decline to less than a high value. Given that

crop removal of P is relatively low for most grain crops, it is important to know

if a field would be unsuitable for waste application, due to high P levels, for this

many years.

b. Allocate On-Farm Nutrients in Accordance with the Budget

Once a nutrient budget is constructed, P-deficient fields can be identified and

preferentially used as sites for land application of manures and litters. If an

overall P excess exists, as is true for many animal-based operations, alternative

methods for utilization of animal wastes must be conceived, designed, and implemented. It may even be possible to prepare long-term plans that anticipate,

based on actual soil test values, when certain fields or areas on a farm will

decline to P levels that require organic waste application to ensure adequate crop




c. Minimize the Use of Unnecessary “Off-Farm” Nutrients

An accurate farm nutrient budget can clearly identify the quantity of fertilizer

or “off-farm’’ waste P required to achieve and maintain an optimum level of soil

P. In general, for an animal-based operation, the long-term benefits of building

up soil P to high levels with fertilizer P or P from other sources (e.g., sludges or

composts) are debatable. Once soils have reached a desirable maximum level of

soil test P they may no longer be suitable for manure application, forcing farmers

to develop prematurely alternative end uses for on-farm wastes. Conversely, crop

production on soils testing low or medium in P may result in reduced yields in

the near term if P fertilizers are not used. It is also possible that the use of small

quantities of P in “starter” fertilizers may produce increases in crop yields even

in soils that have high soil test levels of P.

d. Implement and Evaluate Appropriate Conservation Measures

In addition to maintaining soil P at an optimum, but not excessive, level,

farmers should implement the conservation measures necessary to prevent P loss

by erosion and runoff. Although many farmers are familiar with and use some

form of reduced tillage, the expertise and desire to implement more laborintensive and expensive conservation measures, such as grassed borders around

field edges, is often lacking. Additionally, research on the value of these conservation measures has sometimes produced conflicting results. Sediment loss is

frequently reduced by no-tillage, but soluble P losses may be enhanced due to

buildups of P in surface horizons. Failing to incorporate manures, as required

by no-tillage, may enhance P losses from these wastes, as discussed earlier

(Table VI). This emphasizes the need for regulatory and advisory agencies that

compel farmers to assume the costs and loss of land associated with conservation

practices to assume the obligation to evaluate thoroughly the performance of

these practices under field conditions.

e. Refine and Utilize Monitoring Techniques

There is a serious need to improve soil testing programs for P to achieve

environmental, as well as agronomic, ends. As previously mentioned, many soil

testing laboratories do not determine or report the actual value of extractable P.

This presents a serious problem for individuals monitoring soils-i.e., how high

is a “high” soil test, and at what level of extractable P is regulation of organic

waste application implemented? Beyond this is the fact that, while some studies

have shown that soil test extractable P may be well correlated with bioavailable

P (Wolf et al., 1985), soil test extractants are at best crude estimates of potentially desorbable P. Further, a soil test extractant provides no real estimate of the

capacity of the soil to sorb additional P. Other types of “soil tests” for P that

bear further investigation include dilute salt solutions to estimate soluble P; P

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