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II. Poultry Wastes: Production and Characteristics
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.
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-
r Bird cages
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).
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
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
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,
Summary of Several Studies Documenting the Elemental Composition of Poultry Manures and Litters"
Content ( 8 )
~ o u ~ t rlitter'
0.4- I . I
0.5- I .2
0.5- I . I
1 . 1 -2.7
0. I- I .5
0. I - 5 . 1
"All data reported on dry weight basis.
'Overcash ef u / . (1983b).
'Stephenson e1 a / . (1990).
eV. A . Bandcl (personal communication. 19891.
POULTRY WASTE MANAGEMENT
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-
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
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
POULTRY WASTE MANAGEMENT
Statewide Nutrient Budge for Delaware, Illustrating the Magnitude
of the Nutrient Management Problems of the Poultry Industry
Nutrient generated or used (mg),
Source or use
Nutrient use by crop
Corn (69,700 ha)
Soybeans (80,600 ha)
Wheat (24,300 ha)
Barley (10,900 ha)
Vegetables (32,400 ha)
Annual nutrient balance
Per hectare (kg)
+ 35 10
“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
J. T. SIMS AND D. C. WOLF
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
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
A. FORMSIN POULTRY
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
Figure 4 Forms and fates of N in poultry wastes.
J. T. SIMS AND D. C. WOLF
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.
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
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