**2. Metal contents of chicken litter**

**1. Introduction**

26 Organic Fertilizers - From Basic Concepts to Applied Outcomes

the Washington Department of Agriculture.

cation is limited [3].

its disposal represents a growing problem for the poultry industry.

such as Primera 3–3–3 crumbles and Primera 4–3–4 crumbles.

An organic fertilizer is a soil amendment produced from plant materials and/or animal manures containing low levels of nitrogen (N), phosphorus (P), potassium (K), and some residues of micronutrients compared with synthetic chemical fertilizers. These plant byproducts include alfalfa meal or pellets (also used as animal feed), corn gluten meal (with allelophatic proper‐ ties), cottonseed meal, and soybean meal (also used as animal feed). Animal byproducts include bat guano, blood meal (slaughterhouse waste product), bone meal, feather meal, enzymatical‐ ly digested hydrolyzed liquid fish, fish emulsion, fish meal, and fish powder. In addition to these byproducts, compost of organic materials (mixture of leaves, food waste, and/or animal manures) and seaweed (valued for its micronutrient contents) are used as organic fertilizers. Contrary to synthetic chemical fertilizers for which nutrient contents are regulated, the term organic fertilizer is not regulated; theses organic fertilizers act as nutrients for plants and soil conditioners that feed soil microorganisms. Biosolids are another type of organic amendment or fertilizer used in agriculture. The United States Environmental Management Agency (USEPA) defines the term biosolids as treated sewage sludge that meets the USEPA pollutant and pathogen requirements for land application as well as surface disposal. As stated early, the term organ‐ ic fertilizer is not regulated and therefore should not be confused with selected organic substances approved by the United States Department of Agriculture (USDA) for its National Organic Program (NOP) for use in organic production. An organic substance to be allowed in certified organic production must be approved by the Organic Materials Review Institute (OMRI) and

In the southeastern states of the United States, the disposal of vast amounts of organic fertil‐ izers in the form of animal waste can otherwise be used as organic fertilizer. More than 65% of US broiler production is concentrated in the southeastern states. In 2012, Alabama ranks second in the United States in broiler production and produced over 1 billion birds [1]. The litter that results annually from this broiler production averages 15 million metric tons, and

In 2010, cash receipts in Alabama from poultry operations made up 68% of the total cash receipts for all commodities [2]. Mineralization of C, N, P, and S in poultry litter added to soil is the main cause of groundwater contamination in areas where mineral fertilizer appli‐

In Alabama, there are only a few companies that transform raw poultry litter into organic fertilizers. MigthyGrow, Inc., produces OMRI approved organic fertilizers (4–3–4) as well as an AgBlend all-purpose fertilizer (3–3–3). Denali Organics, LLC, uses catfish byproducts with a proprietary digestive enzyme to produce an organic liquid fertilizer that can be topdressed, banded with seeds, or foliar sprayed. Gulf Coast Organic is a distributor of liquid fertilizers such as Gator Perform SRN (30–0–0) for lawns, turf, and golf courses, and food crops, Primera one green fee super (15–0–0), Turf balance RSN (12–0–12), Medina has a Gro plant (6–12–6), and Medina hasta Gro lawn (12–4–8). It also distributes granular fertilizers Variations in trace element contents of chicken litter have been reported. These variations are attributed to trace elements contained in ingredients fed to chicks (feedstuffs, drugs, feed spillage, and drinking water). Compounds and elements added to chicken diets to stimulate growth and feed efficiency include arsenilic acid, copper sulfate in addition to argon, cadmium, calcium, chlorine, cobalt, cerium, dysprosium, iron, lanthanum, manganese, samarium, selenium, titanium, uranium, vanadium, and zinc [5–8]. Moreover, for disease resistance, more than 20 antibiotics are often added to animal diets. All these elements and compounds have been found at elevated concentrations in chicken litter because those are not completely metabolized in their digestion system. Investigation of 33 chicken litter samples from 12 Alabama counties showed large variations in barium (0.014–0.038 g/kg), calcium (18.9–40.2 g/ kg), magnesium (4.8–10.0 g/kg), potassium (18.1–36.5 g/kg), and sodium (3.6–9.2 g/kg). Means of these elements [9] are shown in **Table 2**. Although these means are similar to those previ‐ ously reported for 106 broiler litter samples from Alabama, USA [9], they are not comparable to those published for Georgia, USA [10] where 86 samples were analyzed. Differences in these results could be attributed to variations in chicken diets in Alabama and Georgia. Other investigators [8, 10–14] confirmed that concentrations of trace elements in animal waste depend on animal diets. The concentration of arsenic in the Alabama samples varied consid‐ erably (<2.0–70.4 mg/kg) with a median of 19.1 mg/kg and a mean of 20.6 mg/kg (**Table 2**). However, at a detection limit of 2.0 mg/L, no arsenic was found in four samples reported in Alabama.


*a n* = 33; samples digested using the microwave-assisted acid digestion EPA 3052 method (adapted from Kpomblekou A et al., 2002).

**Table 2.** Range, median, and mean of trace and nontrace elements in chicken litter samples generated in Alabama.

Exposure of Cd to animals and humans at relatively high levels in food, water, or air has caused harmful effects. Almost all the samples tested did not contain or contained only trace amounts of Cd and varied from <0.2 to 1.7 mg/kg. Other researchers reported concentrations of 1 mg Cd/kg [15] and 6 mg Cd/kg [8] in single samples of chicken litter. Similarly, only trace amounts of Co were detected in the samples with a mean of 0.4 mg/kg (Table 2). The presence of Cr in the ecosystem must be carefully monitored. Chromium concentrations in tested samples in Alabama range from <2 to 17.6 mg Cr/kg with a median of 3.2 mg Cr/kg. Concentrations of other trace elements (Cu, Fe, Mn, Mo, Ni, Se, and Zn) are shown in Table 2 as well. The most abundant elements found in chicken litter are Cu (211–840 mg/kg), iron (718–6691 mg/kg), and manganese (254–720 mg/kg). Copper, Fe, and Zn are the most widely studied trace metals in chicken litter, probably because of their possible toxic effects on crops. In soils receiving excessive applications of chicken litter with high P content, there exists a possible P-induced Zn deficiency. At detection limits of 0.2 and 2.0 mg/L, no measurable amounts of Ag and Pb, respectively, were found in chicken litter.

**Total elemental contenta Range Median Mean**

 Aluminum 0.4–8.4 1.4 2.2 Barium 0.014–0.038 0.025 0.024 Calcium 18.9–40.2 27.3 26.6 Magnesium 4.8–10.0 6.1 6.3 Potassium 18.1-36.5 25.9 25.5 Sodium 3.6–9.2 7.1 6.9

 Arsenic <2.0–70.4 19.1 20.6 Cadmium <2.0–1.7 <0.2 0.3 Cobalt <2.0–2.3 <0.2 0.4 Chromium <2.0–17.6 3.2 3.7 Cupper 211–840 410 450 Iron 718–6691 1596 2073 Manganese 254–720 356 388 Molybdenum <2.0–4.9 0.2 0.9 Nickel <2.0–25.1 1.0 5.2 Selenium <2.0–24.3 <2.0 5.5 Zinc 224–706 371 399

*n* = 33; samples digested using the microwave-assisted acid digestion EPA 3052 method (adapted from Kpomblekou A

Exposure of Cd to animals and humans at relatively high levels in food, water, or air has caused harmful effects. Almost all the samples tested did not contain or contained only trace amounts of Cd and varied from <0.2 to 1.7 mg/kg. Other researchers reported concentrations of 1 mg Cd/kg [15] and 6 mg Cd/kg [8] in single samples of chicken litter. Similarly, only trace amounts of Co were detected in the samples with a mean of 0.4 mg/kg (Table 2). The presence of Cr in the ecosystem must be carefully monitored. Chromium concentrations in tested samples in Alabama range from <2 to 17.6 mg Cr/kg with a median of 3.2 mg Cr/kg. Concentrations of other trace elements (Cu, Fe, Mn, Mo, Ni, Se, and Zn) are shown in Table 2 as well. The most abundant elements found in chicken litter are Cu (211–840 mg/kg), iron (718–6691 mg/kg), and manganese (254–720 mg/kg). Copper, Fe, and Zn are the most widely studied trace metals in chicken litter, probably because of their possible toxic effects on crops. In soils receiving excessive applications of chicken litter with high P content, there exists a possible P-induced

**Table 2.** Range, median, and mean of trace and nontrace elements in chicken litter samples generated in Alabama.

Nontrace element g/kg

28 Organic Fertilizers - From Basic Concepts to Applied Outcomes

Trace element/micronutrient mg/kg

*a*

et al., 2002).

The use of chicken litter in agriculture as an organic fertilizer is not without challenges. The trace elements in the litter can accumulate in topsoil over time, can become a source of surface water pollution via water runoffs following storm events and depending on soil characteristics, and the elements may contaminate groundwater and may become bioavailable and phyto‐ toxic. Soil profile samples taken in selected Alabama soils demonstrate that depending on soil types the trace elements can move through soil profiles. Differences in Cr concentrations in Alabama amended and nonamended soils with chicken litter exceed 40 mg/kg at 45–60 cm and 60 mg/kg at 60–75 cm. This strongly suggests that Cr is fairly mobile in these soils. For example, in Fuquay and Madison soils, the increased Cr concentration in the amended soils over the nonamended soils at 90 cm depth exceeded 10 and 30 mg/kg, respectively (**Figure 1**). Just like Cu and Ni, chromic (Cr3+) forms of Cr are strongly complex with soil organic matter as well as chemisorbs on sexquioxides and therefore immobile in soils. Chromate (CrO4 2−) although more toxic than Cr3+ is less adsorbed and displays more mobility in soils under favorable environmental conditions. A complete different picture was obtained for cadmium in the soil profiles (**Figure 2**). A background concentration of Cd above 0.5 μg/g soil has been attributed to anthropogenic activities [16]. The cadmium concentration in the soils was relatively low (<5.63 mg/kg) with the exception of Madison soil where the Cd concentration achieved 10.2 mg/kg at 45 cm depth. The addition of poultry litter to Orangeburg soil did not change the Cd concentration it its profile. Mobility of trace elements in soil has been associated with presence of organic matter [17] For the mobility of other trace elements in Alabama soils, the reader is referred to Cadet et al. [18].

**Figure 1.** Mobility of Cr in benchmark Alabama soils after long-term poultry litter addition. \*, \*\*, \*\*\* indicate signifi‐ cance at 0.05, 0.01, and 0.001 levels of probability, respectively. NS: not significant at depth specified. From Cadet et al., 2012 [18].

**Figure 2.** Mobility of Cd in benchmark Alabama soils after long-term poultry litter addition. \*, \*\*, \*\*\* indicate signifi‐ cance at 0.05, 0.01, and 0.001 levels of probability, respectively. NS: not significant at depth specified. From Cadet et al., 2012 [18].

#### **3. Nitrogen contents of chicken litter**

As organic fertilizer, chicken litter is valued because it contains macro- and micronutrients. A large majority of nitrogen in the litter (a mixture of chicken manure and bedding materials) exists in organic forms. Ammonium, NH4 + –N; nitrate, NO3 − –N; and nitrite, NO2 − –N represent‐ ing the inorganic form are found in small but sometimes significant amounts. This is especially true when chicken litter is stockpiled under environmental conditions conducive to nitrifica‐ tion (oxidation of NH4 + –N to NO3 − –N via NO2 − –N). Failure to take this increase in N into account will lead to an underestimation of the total N in chicken litter.

#### **3.1. Total nitrogen contents of chicken litter**

The NO3 − –N and NO2 − –N contained in environmental samples are not recovered quantitatively by the regular Kjeldahl digestion procedure. A set of modifications of the regular Kjeldahl procedure have been developed to include NO2 − –N and/or NO3 − –N in soil and plant materials. As pretreatment, before Kjeldahl digestion, Asboth [19] reacted benzoic acid with nitric acid. Following this first attempt, several pretreatments of samples containing NO3 − –N have been suggested: phenolsulfuric acid [19], ferrosulfate [20], NaOH solution, and Devarda's alloy to reduce NO3 − - and NO2 − –N to NH4 + –N with its subsequent distillation into a receiving flask containing concentrated H2SO4 [21], ferrum reductum [21], whereas KMnO4 was used successfully to oxidize NO2 − –N to NO3 − –N and then ferrum reductum to reduce NO3 − –N to NH4 + –N, which was then followed by the Kjeldahl digestion [22]. The most widely used modifications today include the salicylic acid–thiosulfate modification method [23], the alkaline reduction modification method [24], and the permanganate-reduced iron modifica‐ tion method [25]. There are serious doubts about the ability of the salicylic acid–thiosulfate method to recover NO2 − –N quantitatively, especially in undried soils [26]. None of the modifications has shown satisfactory results in recoveries of NO3 − –N and NO2 − –N across a wide range of soils and plant materials. The permanganate-reduced iron modification does not give satisfactory results for samples containing organic matter that resists complete digestion [27]. The underestimation of the total N content of chicken litter may result in its overapplication with potential environmental consequences of surface water eutrophication. On the other hand, an overestimation of the total N may result in its inadequate application.

Statistics of the total N contents of chicken litter samples collected in Alabama and analyzed by various methods are shown in **Table 3**. The most unusual results obtained are those by the Leco-combustion method with an average total N content of 3.78%. This represents an underestimation of the total N by 13.5% as compared with the Devarda's alloy method. This could be attributed to partial oxidation and/or an ineffective oxidation of the samples. As compared with the regular Kjeldahl method, the Leco-combustion method underestimated all the chicken litter samples. The mean of samples by the regular Kjeldahl method was 41 g/kg, whereas that of the Leco-combustion was 37.7 g/kg [28]. One of the consequences of underes‐ timation of the total N in chicken litter is its overapplication that would lead to the accumu‐ lation of nutrients such as nitrates and phosphates in topsoil. When not absorbed by plant roots, these nutrients may find their way into surface waters or groundwaters by percolation through soil profile. Reports [29] also indicated that Leco FP-428 Nitrogen Determinator underestimated N when compared with other methods (the regular Kjeldahl method, the phenyl acetate method, the salicylic acid method, and the NO3 − –N prereduction method). The Leco FP-428 gave lower results of the total N for all the samples (Stockton soil, Copay soil, and in-house liver tissue standard) tested. A study showed that Leco FT-428 and CHN-600 provided slightly higher total N levels than the regular Kjeldahl methods [30]. Dry combustion methods have been widely used in laboratories because the procedures are automated and rapid (analysis time for C, H, and N <5 min/sample by the Leco CHN-600); as many as 80 samples can be performed in 24 h [31]. Seven pretreatments (salicylic acid–Na2S2O3, aqueous Na2S2O3, Devarda's alloy, Zn–CrK(SO4)2, H2O2–Fe, NaOCl–Fe, and KMnO4–Fe) compared with the regular Kjeldahl method showed no significant difference between the N content in fresh manures [32]. The study, however, showed a significant difference between the modified methods and the regular Kjeldahl method in the case of composted poultry manure. It is well known that storage conditions may significantly affect the proportion of ammonium and nitrate in environmental samples. It is important to point out that the samples studied contained between 0.07 and 7.63 g NO3 − –N/kg for poultry manures and the composted poultry manure with wood chips, respectively. Ratios of the total N determined by the KMnO4 method

**Figure 2.** Mobility of Cd in benchmark Alabama soils after long-term poultry litter addition. \*, \*\*, \*\*\* indicate signifi‐ cance at 0.05, 0.01, and 0.001 levels of probability, respectively. NS: not significant at depth specified. From Cadet et al.,

As organic fertilizer, chicken litter is valued because it contains macro- and micronutrients. A large majority of nitrogen in the litter (a mixture of chicken manure and bedding materials)

ing the inorganic form are found in small but sometimes significant amounts. This is especially true when chicken litter is stockpiled under environmental conditions conducive to nitrifica‐

by the regular Kjeldahl digestion procedure. A set of modifications of the regular Kjeldahl

As pretreatment, before Kjeldahl digestion, Asboth [19] reacted benzoic acid with nitric acid.

Following this first attempt, several pretreatments of samples containing NO3

−

−

–N; nitrate, NO3

−

–N contained in environmental samples are not recovered quantitatively

−

–N and/or NO3

–N; and nitrite, NO2

–N). Failure to take this increase in N into

−

–N in soil and plant materials.

−

–N have been

–N represent‐

+

–N via NO2

2012 [18].

The NO3 −

**3. Nitrogen contents of chicken litter**

30 Organic Fertilizers - From Basic Concepts to Applied Outcomes

exists in organic forms. Ammonium, NH4

+

**3.1. Total nitrogen contents of chicken litter**

procedure have been developed to include NO2

−

–N to NO3

−

account will lead to an underestimation of the total N in chicken litter.

tion (oxidation of NH4

–N and NO2

over the regular, the salicylic acid, the Devarda's alloy, or the Leco-combustion method have been published [28]. The KMnO4:Devarda's alloy method mean ratio was 1.01 and implies that these two methods are also similar. Extremely high concentrations of ammonium were reported in the Delaware samples and implies that large portions of the organic N were converted into NH4 + –N with potential to be oxidized to NO3 − –N during storage. If not taking into account, one may expect an overapplication of the chicken litter to topsoil with serious environmental consequences.


*a n* = 33 collected in 12 counties; litter age varied from 4 months to 18 months; bedding materials include: pine shavings, peanut hulls, pine chips, and sawdust (adapted from Kpomblekou A, 2006).

**Table 3.** Range, median, and mean of total N in chicken litter samplesa generated in Alabama and digested by total N determination methods.

#### **3.2. Inorganic nitrogen contents of chicken litter**

Inorganic N found in chicken litter is small and could be extracted with 2 M KCl solution (litter/ solution ratio, 1:20). Following the filtration and centrifugation of the mixture, ammonium–N and (NO3 − + NO2 − )–N in the filtrate could be determined by steam distillation [33] whereas NO2 − –N could be determined by a modified Griess-Ilosvay colorimetric method [34]. Inorganic N contents of the chicken litter can vary significantly and may not be related to chicken litter age or bedding material types [28]. Ammonium is the most dominant inorganic N in chicken litter. The mean NH4 + –N concentrations tested for samples from Alabama ranged from 1.61 to 5.39 g/kg (**Table 4**).

In general, NH4 + –N contents of the samples were higher than those of (NO3 − + NO2 − )–N, which varied from 0.19 to 5.56 g/kg. Under the storage conditions (4 ± 1°C) nitrification was effectively reduced. However, (NO3 − + NO2 − )–N contents of animal waste may be greater than those of NH4 + –N [28]. Nitrite does not usually accumulate in animal waste because it is rapidly oxidized to NO3 − unless its oxidation is inhibited by environmental conditions. Nitrite concentrations could vary from 0 to 0.58 g/kg in a sample, therefore one should not be very much concerned about the recovery of NO2 − –N in chicken litter analysis since its concentration is negligible. Ammonium concentration may vary from 3.49 to 16.4% for total Kjeldahl-N and could totally be recovered in samples by almost all total N determination methods. On the other hand, the (NO3 − + NO2 − )–N content cannot be ignored. It represents 0.44–11.4% of the total organic N in chicken litter. A range of 60–97% and 3–40% of the total N in animal manures were reported present as organic and inorganic N, respectively [32]. The authors also reported that most of the inorganic N was in the form of NH4 + –N (77–89%) with only a small fraction present in NO3 − –N (6–12%) and NO2 − –N (0.2–2%). Bedding materials seem to influence the inorganic N content of the litter. The mean values of the total N (53.2 g/kg), NH4 + –N (20.6 g/kg), and NO3 − – N (308 mg/kg) were reported in 20 poultry manures collected from stockpiled manure and poultry houses in Delaware [35]. The following trend has been reported for Alabama bedding materials: pine chips (6.29 g N/kg) > pine shaving (5.34 g N/kg) > sawdust (4.53 g N/kg) > peanut hulls (4.32 g N/kg) > mixture pine shavings–sawdust (3.41 g N/kg) [28].

over the regular, the salicylic acid, the Devarda's alloy, or the Leco-combustion method have been published [28]. The KMnO4:Devarda's alloy method mean ratio was 1.01 and implies that these two methods are also similar. Extremely high concentrations of ammonium were reported in the Delaware samples and implies that large portions of the organic N were

into account, one may expect an overapplication of the chicken litter to topsoil with serious

*n* = 33 collected in 12 counties; litter age varied from 4 months to 18 months; bedding materials include: pine shavings,

Inorganic N found in chicken litter is small and could be extracted with 2 M KCl solution (litter/ solution ratio, 1:20). Following the filtration and centrifugation of the mixture, ammonium–N

–N contents of the samples were higher than those of (NO3

varied from 0.19 to 5.56 g/kg. Under the storage conditions (4 ± 1°C) nitrification was effectively

could vary from 0 to 0.58 g/kg in a sample, therefore one should not be very much concerned

Ammonium concentration may vary from 3.49 to 16.4% for total Kjeldahl-N and could totally be recovered in samples by almost all total N determination methods. On the other hand, the

chicken litter. A range of 60–97% and 3–40% of the total N in animal manures were reported

–N [28]. Nitrite does not usually accumulate in animal waste because it is rapidly oxidized

unless its oxidation is inhibited by environmental conditions. Nitrite concentrations

)–N content cannot be ignored. It represents 0.44–11.4% of the total organic N in

–N could be determined by a modified Griess-Ilosvay colorimetric method [34]. Inorganic N contents of the chicken litter can vary significantly and may not be related to chicken litter age or bedding material types [28]. Ammonium is the most dominant inorganic N in chicken

)–N in the filtrate could be determined by steam distillation [33] whereas

–N concentrations tested for samples from Alabama ranged from 1.61 to

)–N contents of animal waste may be greater than those of

–N in chicken litter analysis since its concentration is negligible.

peanut hulls, pine chips, and sawdust (adapted from Kpomblekou A, 2006).

**Table 3.** Range, median, and mean of total N in chicken litter samplesa

**3.2. Inorganic nitrogen contents of chicken litter**

+

− + NO2 −

−

+

reduced. However, (NO3

about the recovery of NO2

**Total N determination method Range (%) Median (%) Mean (%)** Regular Kjeldahl 2.75–5.49 4.22 4.10 Potassium permanganate-reduced iron 2.93–5.71 4.42 4.35 Salicylic acid 3.02–5.24 4.11 4.09 Devarda's alloy 3.11–5.52 4.30 4.37 Leco-combustion 2.57–5.01 3.83 3.78

−

–N during storage. If not taking

generated in Alabama and digested by total N

− + NO2 −

)–N, which

–N with potential to be oxidized to NO3

converted into NH4

determination methods.

− + NO2 −

litter. The mean NH4

5.39 g/kg (**Table 4**).

In general, NH4

and (NO3

NO2 −

NH4 +

to NO3 −

(NO3 − + NO2 −

*a*

environmental consequences.

+

32 Organic Fertilizers - From Basic Concepts to Applied Outcomes


*a n* = 33 collected in 12 counties; litter age varied from 4 months to 18, and bedding includes: pine shavings, peanut hulls, pine chips, and sawdust.

b Ammonium–N and nitrate–N were determined in 2 M KCl filtrate by steam distillation (Keeney and Nelson, 1982) whereas nitrite–N was determined by a modified Griess-Ilosvay colorimetric method (Barnes and Folkard, 1951) (adapted from Kpomblekou A, 2006).

**Table 4.** Range, median, and mean of inorganic N in chicken litter samplesa generated in Alabama.

#### **3.3. Mineralization of organic nitrogen in chicken litter**

Organic N to become available for plant uptake must be mineralized. The mineralization of organic N depends on several factors: soil types and litter bedding materials that could significantly alter N transformation in soils. Organic N mineralization in the 10 soils (amended or not) tested was best described by first-order kinetics, but the decomposition rates and halflife of remaining N vary significantly indicating that fractions of organic N in the chicken litter samples differ (**Table 5**). **Table 5** also shows that the decomposition was also affected by soil types.


*a k*1 and *k*2 were calculated from graphs prepared by plotting organic N remaining after each incubation time against time. No second phase was identified in Sucarnoochee and Cecil soils amended with broiler litter 2. From Kpomblekou-A and Genus, 2012.

**Table 5.** First-order rate constants for decomposition of organic N in soil alone and broiler titter-amended soils.

#### **3.4. Total and inorganic phosphorus contents of chicken litter**

Broilers are typically fed corn–soybean blend mix fortified diets with vitamins and minerals. Corn and soybean meal contain on average 1.88 and 3.88 g/kg phytate-P, corresponding to 71.6 and 59.9% of the total P in their grains, respectively. Because broilers in their digestive system lack phytase, an enzyme that splits P from the phytate molecule, P of the grain is not absorbed by the birds and therefore released into chicken manure. The reduction of nonphytate P and utilization of phytase enzymes to hydrolyze phytic acid in corn grains fed to poultry birds enabled a significant decrease in the total P in litters by 3.4–8.8 g/kg relative to normal diets [35]. The hydrolysis of phytate by addition of phytase to animal feeds increases endogenous P availability. Phytase addition not only increases P absorption and promotes healthy broiler growth, but also saves money that could have been spent on supplement P in broiler diets. Although enzymes have been successful in catalyzing the hydrolytic degradation of phytic acid and its salts, their high anticipated production costs have not convinced producers of their use as a suitable profitable alternative.

**Soil series Broiler litter**

*a*

Kpomblekou-A and Genus, 2012.

**sample ID**

34 Organic Fertilizers - From Basic Concepts to Applied Outcomes

**Decomposition rate (week−1) a**

Appling None 0.00132 0.0003 6.73 1.38 75 Cecil None 0.0127 0.0019 3.54 2.01 52 Colbert None 0.004 0.002 2.27 1.34 50 Decatur None 0.003 0.001 6.03 1.57 33 Dothan None 0.006 0.002 3.80 1.78 50 Hartsells None 0.0015 0.0006 1.85 0.78 66 Linker None 0.007 0.003 5.10 0.37 33 Maytag None 0.0105 0.0016 4.15 1.43 62 Sucarnoochee None 0.012 0.001 4.68 2.31 38 Troup None 0.0025 0.0026 2.49 0.95 40 Appling 1 0.0065 0.0023 18.8 1.10 15 Cecil 1 0.0026 0.0014 17.7 1.86 38 Colbert 1 0.0038 0.0025 18.2 3.32 26 Decatur 1 0.004 0.0018 11.3 2.40 25 Dothan 1 0.0028 0.0015 14.1 1.25 35 Hartsells 1 0.003 0.0014 20.7 2.29 33 Linker 1 0.0036 0.0012 20.4 2.32 28 Maytag 1 0.0044 0.0015 19.7 2.43 23 Sucarnoochee 1 0.003 0.0029 17.5 – 33 Troup 1 0.0023 0.00115 5.55 1.37 43 Appling 2 0.0039 0.0012 51.1 1.49 25 Cecil 2 0.0028 0.0014 29.9 – 35 Colbert 2 0.0031 0.0021 19.7 3.49 32 Decatur 2 0.0045 0.002 17.8 3.41 22 Dothan 2 0.0029 0.0018 33.7 1.56 34 Hartsells 2 0.0043 0.0021 28.6 2.69 23 Linker 2 0.0035 0.0014 26.6 2.58 28 Maytag 2 0.0044 0.0013 35.3 2.36 23 Sucarnoochee 2 0.0049 0.0018 28.7 2.93 20 Troup 2 0.0025 0.00095 18.5 1.29 40

**Percentage of N mineralized at each phase**

*k***<sup>1</sup>** *k***<sup>2</sup>** *D***<sup>1</sup>** *D***<sup>2</sup>**

*k*1 and *k*2 were calculated from graphs prepared by plotting organic N remaining after each incubation time against time. No second phase was identified in Sucarnoochee and Cecil soils amended with broiler litter 2. From

**Table 5.** First-order rate constants for decomposition of organic N in soil alone and broiler titter-amended soils.

Broilers are typically fed corn–soybean blend mix fortified diets with vitamins and minerals. Corn and soybean meal contain on average 1.88 and 3.88 g/kg phytate-P, corresponding to 71.6 and 59.9% of the total P in their grains, respectively. Because broilers in their digestive system

**3.4. Total and inorganic phosphorus contents of chicken litter**

**Half-life of N remaining (weeks)**

> Thus, a major portion of phosphorus (P) in chicken litter originates from phytic acid and its phytate salts. The total P content of chicken litter (*n* = 33) sampled in Alabama varied between 1.58 and 3.20%. Fractions of the P removed by sequential extraction showed that they contain 29.5, 32.5, and 38.0% of organic, inorganic, and residual P, respectively (**Figure 3**). The organic fraction (**Figure 4**) contains sodium bicarbonate soluble-Po (44.6%), microbial-Po (27.2%), and sodium hydroxide soluble-Po (28.2%). The inorganic P (**Figure 5**) is made of water soluble-Pi (40.2%), sodium bicarbonate soluble-Pi (10.1%), microbial-Pi (2.85%), sodium hydroxide soluble-Pi (2.83%), and hydrochloric soluble-Pi (44.0%). Although broiler litter is an excellent soil amendment that improves soil fertility of farmers' fields, its high P content puts broiler litter amended soils at risk and susceptible to P accumulation. Applications of chicken litter have resulted in accumulation of P in topsoil and its movement to depths. Results of studies conducted on six soils of southern Alabama showed a significant increase in the total P (**Figure 6**). The total P concentrations are higher in the chicken litter-amended soils than in their nonamended counterparts. In Bonifay soil, however, throughout the profile the total P concentration was higher in the nonamended soil than the broiler litter-amended soil. In many cases, the observed differences were statistically (*P* < 0.05) significant. In Fuquay soil, the application of chicken litter increased the total P concentrations from 263 to 835, 165 to 805, 121 to 244, and 153 to 1555 in the 15–30, 30–45, 45–60, and the 60–75 cm depths, respectively. Madison soil showed that the total P concentrations in the chicken litter amended soils were significantly different from the nonamended soils throughout the soil profile. The Bray 1-P concentrations (**Figure 7**) were ≦10 mg/kg for Madison and Malbis soils, <40 mg/kg in Orangeburg soils, and >75 mg/kg in the Bonifay, Dothan, and Fuquay soils. The Bray-1 extractable P accumulated in the 0–15 cm depth of each of the six soils following broiler litter application. Bonifay, Fuquay, Malbis, and Orangeburg soils showed accumulation throughout the profile and decreased as depth increases. Dothan and Madison soils showed an accumu‐ lation only in the 0–15 cm depth, but the accumulation was not significant in Madison topsoil. Bonifay and Orangeburg soil showed considerable accumulation down to 45 cm, but the accumulation was significant (*P* < 0.05) only at the 0–15 and 15–30 cm depths. Fuquay soil showed significant accumulation throughout the soil profile, and Malbis and Orangeburg soils showed similar trends. Elevated Bray 1 soil test P levels following a long-term application of manures and wastes have been reported [36]. The study found that several Oklahoma soils receiving a long-term application of broiler litter reported Bray 1 soil test several P levels up to 279 mg/kg.

**Figure 3.** Average P fractions removed by sequential extraction from broiler litter.

**Figure 4.** Average organic P fractions removed by sequential extraction from broiler litter.

Organic Fertilizers in Alabama: Composition, Transformations, and Crop Response in Selected Soils of the Southeast United States http://dx.doi.org/10.5772/63084 37

**Figure 5.** Average inorganic P fractions removed by sequential extraction from broiler litter.

**Figure 3.** Average P fractions removed by sequential extraction from broiler litter.

36 Organic Fertilizers - From Basic Concepts to Applied Outcomes

**Figure 4.** Average organic P fractions removed by sequential extraction from broiler litter.

**Figure 6.** Distribution of total P in poultry littered (open circle) and nonlittered (open triangle) soils. Adapted from Dotson, 2000.

**Figure 7.** Distribution of Bray 1-P in poultry littered (open circle) and nonlittered (open triangle) soils. Adapted from Dotson, 2000.

The USEPA required Concentrated Animal Feeding Operations (CAFO) to develop and implement Best Management Practices that minimize phosphorus and nitrogen transport from fields to surface waters. The standard requires soil phosphorus not to exceed 200 ppm by 2018 and soil with greater than 400 ppm not to receive any poultry litter applications. It is in light of these requirements of the CAFO regulations that emerged the need to develop a chemical method that would reduce phosphorus content of poultry litter before its application to agricultural land in order to avoid a long-term builds up of phosphorus in soil. An extraction procedure was developed at Tuskegee University and includes steps of equilibrating an amount of chicken litter with an extracting solution [37]. After a contact time, the solution removes a significant amount of the phosphorus from the chicken litter. The chicken litter is then separated from the solution to obtain phosphorus-depleted chicken litter. Phosphorus contained in the phosphorus-rich solution can be precipitated and recovered to fertilize soils that are phosphorus-depleted. The extracting solutions proposed removes excess quantities of phosphorus (about 90%) in the chicken litter while retaining other essential elements (e.g., carbon, nitrogen, and sulfur) needed for plant growth and development.
