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II. Poultry Wastes: Production and Characteristics

II. Poultry Wastes: Production and Characteristics

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14



J. T. SIMS AND D. C. WOLF



agement of any poultry waste begins with an understanding of its composition

and the physical, chemical, and microbiological reactions that control the fate of

potential pollutants in the waste following land application. Simpson (1990) recently reviewed the topic of agricultural use of poultry wastes and identified the

three most common poultry wastes as (1) poultry manure (urine and feces) or

poultry litter (a mixture of manure and the woodchips used as a base in broiler

houses), (2) dissolved air flotation (DAF) sludge originating from poultry processing plants, and (3) composts produced from hatchery wastes and dead birds.

Wastewaters from poultry processing plants are also commonly applied to agricultural lands, but these operations are relatively small in magnitude relative to

programs that involve land application of manures, litters, sludges, and composts. Wastewater irrigation also normally requires strict adherence to regulations established by state environmental agencies. Limited information is available on the nature and use of wastewaters, DAF sludges, and poultry composts.

Consequently, our discussion will focus on the production and composition of

poultry manure and litter, although some information on dead poultry composts

will be provided because of the emerging importance of this issue.



A. POULTRY

PRODUCTION

OPERATIONS

AND TYPES

OF WASTE

The major poultry production operations include broiler chickens, turkeys,

and eggs (layer chickens). Broilers account for approximately 80% of the poultry

meat produced in the United States and 72% of the production on a worldwide

basis (Economic Research Service, 1992). Other types of poultry operations include breeders, used to produce eggs for broiler and layer operations; pullet

replacement operations that produce chickens for layer and breeder operations;

and miscellaneous poultry such as ducks, geese, and pigeons. The production

facilities used for all poultry operations are similar and, for all practical purposes, today consist solely of total confinement housing. Some limited semiconfinement or free-range poultry operations exist, but from a poultry waste

management perspective, the vast majority of manures, litters, sludges, and

composts originate from broilers, layers, and turkeys produced in total confinement housing.

Two types of confinement housing are commonly used for poultry operations:

(1) caged pit systems and (2) floor/litter systems. A variety of confinement designs exist, but the houses illustrated in Fig. 2A are reasonably typical examples

of these two systems. Caged pit systems are most commonly used for layer or

pullet operations and consist of cages suspended above either a deep or shallow

pit. Manure from the birds falls into a pit, where it is removed periodically by

scraping or flushing. Caged pit manure contains no bedding material and is nor-



,



Solid

manure

spreader



A

r Bird cages



v-



A



2



1



Solid

manure

/spreader



Figure 2 Typical (A) confinement systems and (B)storage structures for a poultry operation.

Adapted from Soil Conservation Service (1992) and Sims er al. (1989).



16



J. T. SIMS AND D. C. WOLF



mally semisolid or liquid in nature, depending on the type of removal system

used. Floor systems are used for broilers, turkeys, or pullets and are normally

single-story houses with an earth or concrete floor covered with from 5 to 15 cm

of a litter material such as sawdust, wood chips, or other carbonaceous substance. The litter acts to absorb moisture, which in turn reduces the incidence of

disease and helps maintain poultry health. A partial cleaning of wet, crusted, or

“caked” litter normally occurs after each flock is removed from the house. A

complete cleanout and replacement of the litter is done less frequently, usually

between 12 and 24 months after introduction of the original litter material.

Once removed from the poultry house, manures and litters are often applied immediately; if not, they are stored in roofed structures, tarpaulin-covered

stacks, windrowed piles, or, in the case of liquid manures, in lagoons or in

concrete or steel storage tanks. Concern over the environmental impact of uncovered manure storage piles has resulted in government cost-sharing to provide

roofed storage barns (Fig. 2B) that can maintain the manure or litter in a dry,

easily handled state until the proper time for land application. Storage locations

should be in well-drained areas and sufficiently removed from any surface water

to avoid contamination by runoff. Liquid or semisolid manures normally originate from layer operations. Information on the design and construction of manure

storage facilities is normally available from local or national soil conservation

agencies or cooperative extension. From the perspective of efficient manure use

in agriculture, the primary goals of these structures are to prevent pollution during storage (e.g., leaching, runoff) and to maintain the manure or litter in a form

that allows for uniform application by manure spreaders or injection equipment.

One alternative waste handling and storage technique that is receiving great interest is a “composter” that can be attached to an existing storage structure. The

primary purpose of these composters is to dispose of dead poultry under conditions of normal mortality by composting the birds with straw and manure

(Palmer and Scarborough, 1989). The dead poultry compost can then be combined with other manure and land-applied or handled separatedly if its physical

properties or composition makes it more suitable for certain crops than others.

Knowledge of the quantity of poultry manure or litter produced on a farm or

within a given geographic area is essential for the design of an effective a waste

management program. Although reasonably accurate estimates of the quantity of

fresh manure produced by various poultry types are available, farm-scale or regional estimates are generally lacking. Overcash et al. (1983a) reported that the

average daily fresh manure production for broilers was 87 kg/1000 kg live

weight, and for laying hens was 73 kg/1000 kg live weight (18 and 25 kg/1000

kg live weightlday on a dry weight basis). Converting this to the quantity removed from a typical broiler house or caged pit operation, the values were 20

kg/1000 kg live weight/day for broilers and 11 kgl1000 kg live weight/day for

laying hens in a deep pit operation. As noted by Malone (1992), however, a



POULTRY WASTE MANAGEMENT



17



number of production, handling, and storage factors affect the actual quantity of

manure/litter generated for various poultry types. Among these are feed composition and feed efficiency, the type of bedding, the frequency of crust removal

and total cleanout operations, the number of flocks in a house between replacement of the bedding material, the final live weight of the poultry, and management practices such as type of watering system, house ventilation system, and

floor type (soil versus concrete). He cited estimates of litter production from the

literature and personal communications that ranged from 0.7 to 2.0 dry Mg/ 1000

broilers and an average value of 1.O dry Mg/ 1000 broilers. A recent study on the

quantity and quality of litter produced in Delaware, conducted by Malone et al.

(1992), showed that the amount of broiler litter produced ranged from 1 .O to 1.1

wet Mg/ 1000 birddflock as a function of type of cleanout program used to remove the litter from the poultry house.

It is clear that we can only estimate the amount and timing of manure or litter

production. However, values such as those obtained by Malone et al. (1992) can

be useful in farm and regional management of poultry wastes. As an example,

consider a typical broiler operation on the Delmarva peninsula with five poultry

houses, six flocks per year, and 200 ha of cropland devoted to corn (75 ha),

wheat (25 ha), and the soybeans (100 ha). Broiler litter production from this

operation would be approximately 650 wet Mg/year. If distributed uniformly and

to nonleguminous crops, the application rate of 6 Mg/ha would provide most, if

not all, of the nutrient requirements for this farm. Similar calculations can be

made for different sized farms or for entire counties or regions to determine if

an adequate land base is available to support an existing or expanding poultry

industry.



B. PROPERTIES

AND COMPOSITION

OF POULTRY

WASTES

A large database is available documenting the physical and chemical properties of poultry manures and litters (Barrington, 1991; Bomke and Lavkulich,

1975; Kunkle et al., 1981; Midwest Planning Service, 1985; Overcash et al.,

1983b; Smith, 1973). Very little information is available on the composition of

processing wastes, wastewaters, and composts. As with other organic wastes,

the moisture content, pH, soluble salt level, and elemental composition of poultry manures and litters have been shown to vary widely as a function of type of

poultry, diet and dietary supplements, litter type, and handling and storage operations. A summary of several studies of manure and litter composition is provided in Table 111 to illustrate the magnitude of this variability. Several noteworthy points can be drawn from this table. First, the total N and P contents of

poultry manures and litters are among the highest of all animal manures. Compare the values in Table 111 with typical reported values for total N in fresh beef,



Table 111

Summary of Several Studies Documenting the Elemental Composition of Poultry Manures and Litters"

Content (rnglkg)



Content ( 8 )

Description

of waste

Fresh chicken

manure'

Mean

Range

Fresh turkey

manure'

Mean

Range

~ o u ~ t rlitter'

y

Mean

Range

Broiler litter'

Mean

Range

Broiler litter"

Mean

Range

Broiler littere

Mean

Range

Cape pit

manuree

Mean

Range



NH 4



P



K



S



6.1

3.7-8.8



0.6

0.4- I . I



2.2

I 2-2.9



2.0

1.2-2.7



-



1 .o



-



-



5.2-14.9



0.6-1.3



4.8

2.9-6.1



0.8

0.5- I .2



I .5

0.5-2.4



2.4

1.3-3.2



-



4.0

2.7-6.4



3.5

1.4-6.8



0.9

0.5- I . I



1.6



1 .8



-



0.5-3.5



1 . 1 -2.7



-



3.1

1.3-7.4



4.0

2.3-6.0



-



I .6

0.6-3.9



2.3

0.7-5.2



0.2-0.8



2.3

0.8-6.1



3.9

1.2-7.7



1.1

0.1-2.0



1.9

0.7-3.6



2.4

0.8-4.9



0.1-1.5



2.4

0.7-8.3



4.3

0.3-10.3



1.1

ND-2.5



2. I

0.3-3.8



2.6

0.1-6.7



0.7

0. I- I .5



4.4

I .3-6.5



I .5

ND-2.9



19

0. I - 5 . 1



2.8

0.7-4.7



0.7

0.1-1.5



"All data reported on dry weight basis.

'Overcash ef u / . (1983b).

'Stephenson e1 a / . (1990).

dMalone (1992).

eV. A . Bandcl (personal communication. 19891.



-



0.5



0.7



Ca



Mg



B



cu



N



Mn



Zn



-



-



-



0.6

0.6-0.6



-



-



-



-



-



-



0.4



-



-



-



0.3-0.5



-



-



-



0.5

0.2 -0.9



473

25- 1003



348

125-667



106- 669



0.7

0.1-1.9



377

21-84s



355

88-772



34 1

64-777



2.3

0.3-12.5



I .o

0.1-2. I



25 I

2-798



309

55-717



338

23-798



10.1

0.2-26.7



I .4

ND- 1.5



I60

2- 1053



296

4- 1061



226

10-937



8.1



-



315



POULTRY WASTE MANAGEMENT



19



dairy, horse, and swine manure: 4.2, 3.5,2.4, and 5.2%; or values for total P in

the same manure: 0.9,0.6,0.4, and 1.5% (Sommers and Sutton, 1980). Second,

poultry litter values for N and P are usually lower than those for fresh manure,

reflecting both the losses the occur following excretion of the waste and the

dilution effect from combining manure with carbonaceous materials that are very

low in N and P. Overcash et al. (1983b) reported that the N and P content of

various bedding materials ranged from 0.2 to 0.8% and 0.1 to 0.2%, respectively. Malone et af. (1992) analyzed 14 samples of wood-based litter and found

an average N and P content of 0.3 and 0.02%. Third, NH4-N is a significant

nitrogenous component of poultry manures and fitters, as is uric acid (2.6% in

fresh manure, 0.9% in litter) (Overcash et al., 198313). Uric acid metabolizes

rapidly to N&-N in most soils. The net result of the high NH,-N and uric acid

contents in poultry wastes is a large percentage of N that can be converted to

NO,-N, often within a few weeks. As discussed in more detail in Section 111,

this can increase the likelihood of NO; nitrogen leaching from poultry manureamended soils unless manure/litter is applied in a manner and at a time that

closely matches crop N uptake patterns. Fourth, the use of poultry wastes as soil

amendments for agricultural crops will provide appreciable quantities of all important plant nutrients. As an example, the application of 9 Mgiha of broiler

litter (75% solids), a rate commonly used to meet the N requirement of agronomic crops, will provide approximately 270 kg Niha (70 kg NH,-Niha), 100

kg P/ha, 165 kg/ha of K and Ca, 45 kg/ha of S and Mg, and 2-5 kgfha of Mn,

Cu, or Zn. Typical fertilizer recommendations for nonirrigated corn (yield goal

of 7 Mglha) in the eastern United States, on soils with m ~ i u m

soil tests for all

nutrients, would be 125 kg N/ha, 30 kg P/ha, and 100 kg K/ha. Calcium and

magnesium requirements are normally met by liming, whereas S, B , Mn, Cu,

and Zn are only recommended for certain crops in specific situations known to

cause deficiencies of these elements. As noted earlier, and as shown in this example, the application of poultry manure based on crop N requirements often

provides more of other nutrients than is required by the crop (e.g., an excess of

70 kg Plha). The implications of long-term manure use on the economics of soil

fertility management and potential environmental impacts of excessive soil nutrients are discussed in more detail in Sections IV and VI.

Manure testing can also identify other properties, elements, or compunds that

may have an impact on crop production or the environment. Phytotoxic effects

of manures are relatively uncommon. However, if applied at excessive rates, the

soluble salts, NH4-N, and alkaline nature of most poultry wastes can produce

crop growth problems. Shortall and Liebhardt (1975) reported that broiler litter

rates of 90 Mgiha or greater significantly reduced corn yields due to high soil

salinity levels. Weil et al. (1979) also reported that excessive manure rates

(>50 Mg/ha) reduced germination, emergence, and seedling growth of corn due

to a combina~ionof high soluble salts, NH4-N and nitrite-N. Both of these stud-



20



J. T. SIMS AND D. C. WOLF



ies, however, found that the effects of excessive manure were transitory and were

reduced by normal rainfall and leaching within 1 year. It should be noted, however, that these studies were conducted on well-drained soils in a humid region

(mid-Atlantic United States) where climatic conditions would be conducive to

rapid leaching of salts and nitrification of NH,-N. Poultry manure is normally an

alkaline material, with pH values ranging from 7.5 to 8.5. Its effects on soil pH

can be significant but somewhat contradictory. Sims (1986b) found that addition

of three broiler litters (pH from 8.5 to 8.9) raised the pH of an Evesboro loamy

sand soil (Typic Hapludults) from 6.5 to 7.5 immediately after application, but

that the final soil pH after 20 weeks was about 5.5. The initially high pH could

reduce micronutrient availability, particularly Mn and Zn; the final more acidic

pH that resulted from the nitrification of added and mineralized NH,-N could

cause phytotoxicity from excessive A1 and Mn in some soils.

As mentioned earlier there is limited information available on the presence or

concentration of heavy metals and pesticides in poultry wastes. New instrumentation available to many testing laboratories, such as inductively coupled plasma

(ICP) spectrometers and gas chromatograph-mass spectrometers, is likely to

make multielement and organic compound analyses of manures and litters more

common in the near future, In addition to the results of Kunkle et al. (1981)

mentioned earlier and the data shown in Table 111 for Cu and Zn, some recent

data on the heavy metal content in broiler litter were obtained from ICP spectrometry analyses conducted by North Carolina State University (J. C. Barker,

personal communication). The means (mg/kg), standard deviations, and number

of samples analyzed were as follows: As (26, 19, 11); Cd (0.4, 0.3, 7); Cr

(9, 0.7, 2); Cu (225, 95,458); Hg (0.2, 0.07, 3); Ni (7, 7, 4), Pb (6, 7, 4); Se

(0.2,0.02, 3); and Zn (315, 105,460). All values are expressed on a wet weight

basis and hence represent the actual concentration applied in the field. For reference purposes, the total solids contents of 534 broiler litter samples analyzed

by North Carolina State averaged 78% (range of 58-97%, SD = 6%).These

concentrations can also be compared to maximum metal concentrations recommended for sewage sludges applied to lands. Ritter (1987) summarized these for

the mid-Atlantic region of the United States (in mg/kg, on a dry weight basis)

as follows: Cd (25), Cr (lOOO), Cu (IOOO), Hg (lo), Ni (200), Pb (lOOO), and

Zn (2500). No maximum concentration value was reported for As or Se.



C. APPROPRIATEUSEOF POULTRY

WASTEANALYSES

These studies leave little doubt that poultry manures and litters are valuable

fertilizer materials, although the wide ranges in nutrient composition reported

raise the question of the most effective use of poultry waste analyses. Certainly



21



POULTRY WASTE MANAGEMENT

Table IV

Statewide Nutrient Budge for Delaware, Illustrating the Magnitude

of the Nutrient Management Problems of the Poultry Industry

Nutrient generated or used (mg),

statewide basis

Source or use

of nutrienta



Nitrogen



Nutrient source

Poultry manure

Fertilizer sales



7865

19,275



3495

2955



6990

15,500



Total

Nutrient use by crop

Corn (69,700 ha)

Soybeans (80,600 ha)

Wheat (24,300 ha)

Barley (10,900 ha)

Vegetables (32,400 ha)



27,140



6450



28,940



9760

0

2180

980

3640



940

1085

330

150

435



1560

1810

545

245

725



Total *

Annual nutrient balance

Statewide (Mg)

Per hectare (kg)

-



16,560



2940



4885



+ 10,580

+ 48



+ 35 10

+ 16



+ 24,055



Phosphorus



Potassium



+llO



“Values for source, use, and balance for N, P, and K based on information from the Delaware Department of Agriculture (1992) and Malone et al. (1992), and estimated nutrient requirements using recent

soil test summaries for Delaware.

bTotal area: 217.900 ha.



analyses of poultry manure or litter from well-defined production systems can

help to establish the potential nutrient supply for a farm or region. This is of

economic value because it can help farmers avoid the unnecessary purchase of

commercial fertilizers. Research-based information on the content and availability of nutrients in poultry wastes is needed not only for crop management,

however, but for the development of state or regional land use plans. An example

of a larger scale application of data on waste properties is given in Table IV for

poultry manure use in Delaware. The N, P, and K contents of over 200 manure

samples produced under different management conditions were combined with

actual values of the mass of manure generated to obtain estimates of manure N ,

P, and K production for the state (Malone et al., 1992). Combining these data

with fertilizer sales and reasonable estimates of crop requirements for these nutrients shows the existence of a large surplus of N, P, and K, equivalent to

approximately 48 kg N, 16 kg P, and 110 kg K for every hectare of cropland



22



J. T. SIMS AND D. C. WOLF



Site number

Figure 3 The difference between total N actually applied, based on poultry manure samples

collected during field application, and the amount estimated to be applied based on laboratory analyses of stockpiled manure samples. Results from a 17-site field experiment (Igo er al.. 1991).



in the state. Unfortunately, this is a common situation in areas where animalbased agriculture is concentrated on an inadequate land base (Power and Papendick, 1985; Power and Schepers, 1989). Clearly, a critical need exists for state

and industry cooperation in the development of waste management plans and

infrastructures that focus on the redistribution of excess manure to nutrientdeficient areas.

Recent studies, however, question the use of analyses of stockpiled manure or

litter to determine field level application rates. In one study, the N loading rates

for broiler litter from 17 different on-farm storage areas, estimated from analysis

of stockpiled litter samples, were compared to the actual loading rate based on

analysis of samples collected during application to field corn (Igo et al., 1991).

As shown in Fig. 3, when desired application rates were applied to large field

plots using commercial manure spreaders, overapplication of 10-20 kg N/Mg

of litter commonly occurred, as did underapplication of 5- 10 kg N/Mg. Therefore, the accurate application of a recommended litter rate for corn (-5 Mg/ha),

based on analysis of the wastes, commonly resulted in the application of excess

manure N approaching the total N requirement of the crop (- 100 kg N/ha).

Clearly, an approach more comprehensive than N analysis and equipment calibration is needed to avoid over- or underapplication of N from organic wastes.

Approaches to improve the efficiency of manure and litter use are described in

Section VI.



23



POULTRY WASTE MANAGEMENT



111. NITROGEN MANAGEMENT FOR POULTRY WASTES

Land application of animal waste is an important management practice to recycle nutrients, to improve or maintain soil fertility, and to improve soil biological and physical properties [Council for Agricultural Science and Technology

(CAST), 19921. Historically, the most important nutrient considerations in developing poultry waste application recommendations have been the concentration and availability of N. Due to the common duct for urine and feces elimination in poultry, N levels of poultry waste are generally higher than those of other

livestock wastes.



A. FORMSIN POULTRY

WASTES

The total N present in poultry waste can be separated into four forms (Fig. 4).

Complex forms of organic N in poultry waste include constituents of feathers

and undigested feed. Labile organic N is largely uric acid and urea. Uric acid in

the fresh waste is rapidly hydrolyzed by the enzyme uricase to urea (Fig. 5). The

urea is hydrolyzed by the enzyme urease to form ammoniacal-N. The NH4-N is

the third form of N found in poultry waste. Nitrate, the fourth form, is generally

absent in poultry waste unless the waste has been stored in an aerobic moist

state. The concentration and distribution of these forms of N can vary with the

particle size of various poultry waste components (solid or liquid excreta, woodDECOMPOSITION



Organic N



Complex

Organic N



AMMON



.



[Ammonium



NITRIFICATION



1

Fixation



'



.



Runc,.



Ii

LeaC'



Figure 4 Forms and fates of N in poultry wastes.



J. T. SIMS AND D. C. WOLF



24



Uric acid



Urea



Ammonia



Figure 5 Generalized reaction for the conversion of uric acid to ammonia.



chips, etc.). For instance, studies by Ndegwa et al. (1991) showed that the N

concentration in the fine fraction of poultry litter ( 1 0 . 8 3 mm) was greater than

in larger sized particles.



B. NITROGEN

TRANSFORMATIONS

IN STORAGE

AND HANDLING

The majority of N excreted in poultry manure is in the form of uric acid that

can be rapidly converted to urea and NH,-N if temperature, pH, and moisture

are adequate for microbial activity (Bachrach, 1957; Rouf and Lomprey, 1968;

Siege1 et al., 1975). The hydrolysis reactions result in elevated pH levels that

facilitate NH,-N volatilization (Reynolds and Wolf, 1987b). Losses of NH,-N

from poultry wastes begin to occur immediately after excretion and can be influenced by conditions within the production house. For instance, Weaver and

Meijerhof (1991) found that NH,-N losses from broiler litter became greater as

relative humidity in the house increased.

Nitrogen loss during storage and handling is determined by climatic conditions

and the specific manure management system used. Estimates of N loss range from

10 to 80% of the N excreted (Midwest Planning Service, 1985; Soil Conservation

Service, 1992). For poultry litter stored under roofed facilities, estimated losses

during storage and handling are 30 to 45% of the total N content. For manure

diluted by 250% and held in storage ponds or lagoons, the N loss may be 70 to

80% of the total N in the waste. Maximizing the nutrient value of poultry wastes,

therefore, requires the use of management practices that will optimize N conservation during storage and handling (Barrington, 1991).



C . NITROGEN

LOSSESDUETO DRYINGPOULTRY

WASTES

Drying poultry waste will enhance volatization if the conversion of uric acid

and urea to NH,-N is complete. Oven drying fresh poultry manure from a laying



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